SYSTEM FOR SUPPLYING ELECTRICAL POWER TO PERSONAL ELECTRONIC DEVICES IN A PASSENGER VEHICLE The present invention relates to systems for supplying electrical power to passengers in a vehicle and to vehicles comprising the same. The present invention also relates to methods for delivering power to passengers in a vehicle. In one aspect the invention enables operators of passenger carrying vehicles to reduce the infrastructure and cost surrounding the provision of passenger power delivery systems and methods by removing external enclosures currently used in the art and, as a consequence enabling the supply of power to passengers without occupying valuable space within the passenger envelope while maintaining compliance with regulatory requirements. Travel is an everyday part of life be it on a train, bus, ferry or aircraft. Each sector is supported by multiple carriers all vying for the same business. Longer journey durations increase the demands of the passenger to remain part of the connected environment. These demands may include business services such as email, web browsing, instant messaging and tele-conferences. In other areas passengers may want to relax and be entertained either by media present on their own personal electronic device (PED) or by streaming new content. To maintain connectivity the PED relies on power usually provided in the form of a local power source, either via a direct connection or via the PED’s internal power supply, a battery. As the work load on the PED increases the amount of power required to provide connectivity functions increases. Without access to power the passenger becomes disconnected from daily life and therefore is unable to continue to listen to music, watch videos, communicate to others via audio and/or video or using the PED as a creative source such as within the social media environment or from a professional aspect the completion of tasks including, but not exclusively, text documents, calculation documents, note taking and interactive graphics documents. Furthermore within the context of daily life the PED and its connections to other personal electronic devices is the central repository of most, if not all, transport and transit documentation such as tickets, boarding passes, medical health records, travel documents and payment methods. Being able to have sufficient power to be able to navigate a journey end to end has become an essential part of daily routine. To those ends it has become commonplace for passengers to select a carrier providing the ability to remain connected during all or part of the journey and as such provision of power to sustain connectivity has become an essential element of the service offering of carriers. Within the confines of a passenger carrying vehicle, space is apportioned such that the passenger occupies a seat, the seat may have arms to improve comfort and to delineate ones seat from another. The area in front of the passenger , in most cases, is limited by a structure that may be another seat or it may indeed be a structural wall or bulkhead. In the case where a seat is in front of the passenger there may be provided a fold down tray for the consumption of food or beverages or for the placement of passenger artefacts such as magazines, books or PED’s. In some situations there may be provided a visual display unit for informing and entertaining the passenger during the journey. Below the seat located in front of the passenger may be a void to be used for additional leg/foot space to aid the passengers comfort or as a place for the passenger to house luggage such as briefcases, small suitcases etc. The latter becoming more common place as the cost of carrying luggage on aircraft increases. The number of passengers that can be transported during any journey is a determinant factor in operational economics. In the commercial airline environment other factors also determine the economic viability of the service including the speed at which passengers can embark or disembark the vehicle; any delays can cause the airline to suffer financial penalties. Passengers themselves face financial penalties for having stow-able bags and therefore try to take as much luggage into the cabin as possible. Within this environment aircraft operators and seat designers strive to increase the space within the seat environment to safely store as much luggage as possible while providing the passenger with a comfortable environment. The seat typically comprises soft furnishings for comfort and a hard structure for support and safety. The hard structure in commercial passenger carrying vehicles will be provided with a degree of certification to support its installation within the specific vehicle type. Vehicle types could include, but are not limited to aircraft, buses, railway, waterborne ferries and other pleasure craft. In all cases the structural integrity of the seat is well defined and can only be modified by the addition of, or the removal of portions of the structure including the cutting of holes or the clamping onto of additional equipment. This is specifically true of aircraft seating. To provide better economics seat design continues to seek better ways to achieve a balance between passenger accommodation and luggage stowage; rarely are seats designed from the outset to support passenger power as a fundamental feature. In a tightly regulated environment, such as passenger transport, power provision to a large passenger population within a confined space is complex and frequently does not sit well with the space constraints found within each passenger volume. In larger, multi-aisle transport vehicles designed for long journeys the seating systems tend to be less compact with a greater focus on passenger comfort and not luggage stowage. Power systems designed within the context of these larger passenger environments tends to leverage the installed Inflight Entertainment Systems (IFE) where the power outlets are embedded within the IFE screen arrangement or within the seat back itself and rarely encroaches into the passenger space itself. For the power providers themselves it makes economic sense to leverage the systems and architecture approved and used within the larger vehicles leading to the compromises in the installation due to the physical volumes of equipment to be installed. It is commonplace to find the power outlets, USB and AC, strapped to the frames of the seats compromising leg space, luggage space and indeed both. Passenger seating is expensive to install and maintain, furthermore seat modifications are complex from a regulatory standpoint and can be expensive. As a result the carrier may not update peripheral equipment as readily as they would like thereby creating a disconnect between the services provided by the carrier and the services required by the passenger. There is a need for a method to enable carrier provided equipment to maintain synchronisation with passenger carried Portable Electronic Devices while providing an environment where power can be implemented either at installation of the seats, or subsequently without the need for seat recertification or to compromise the passenger/luggage envelope thereby enabling the passenger to benefit from a system capable of maintaining concurrency with the fast pace of technological improvements within the PED environment and from the carriers standpoint an economic installation of power outlets by reducing costs associated with installation, maintenance and amortisation, There has now been found a way to supply power to a PED in a controlled way within a vehicle which enables the owner of the PED to maintain connectivity while ensuring the safety protocols and procedures for installation within the vehicle, discussed hereinbefore, to be followed. There is now provided a method and system for enabling a passenger in a vehicle, for example a commercial transport vehicle, to receive electrical power for the on-going function of the carry-on Portable Electronic Device (PED) and to recharge the battery commonly installed within. The present invention provides power for the use of passenger carry on devices (Portable Electronic Devices or PEDs), such as Smartphones, tablets and other portable computers, in a resilient, economic and ergonomic manner while maintaining standards required by regulatory authorities. In a first aspect, the present invention provides for an electrical connector comprising one or more receptacles into which the passenger inserts a compatible mating plug having a cable to connect the PED to the vehicle mounted electrical connector in order to receive power from the vehicle mounted power system. According to the present invention, there is provided an electrical power supply assembly for use in a seat assembly of a passenger vehicle, the power supply assembly comprising: an electrical power supply converter assembly having a first connection for receiving electrical power from the electrical system of the vehicle and a second connection for transmitting converted electrical power; and an electrical port assembly comprising a connection for receiving converted electrical power from the second connection of the electrical power supply converter assembly and one or more electrical ports for connecting to the PED of a person. In a further aspect, the present invention provides a seat assembly for a passenger vehicle, the seat assembly comprising: a seat frame comprising a first seat frame member and a second seat frame member; and an electrical power supply converter assembly mounted in or on the first seat frame member and comprising a first connection for receiving electrical power from the electrical system of the vehicle and a second connection for transmitting converted electrical power; an electrical connector assembly mounted in or to the first seat frame member or the second seat frame member and comprising a connection for receiving converted electrical power from the second connection of the electrical power supply converter assembly and one or more electrical ports for connecting to the PED of a person. The present invention further provides a vehicle comprising a seat assembly as hereinbefore described, for example an aircraft. In the conventional case in passenger vehicles, such as aircraft, electrical ports for connecting to PEDs, such as USB ports, are located either in the IFE system housings or provided in separate modules known as Line Replaceable Modules (LRUs). The LRUs are either mounted in the seat backs or mounted into a bespoke housing bolted to the spar tubes or clamped to the legs. The issues with these installations are increased damage to the components, as they are usually in vulnerable positions; they impose space restrictions on the passenger accommodation space; and provide for lower than optimum heat dissipation as the electronic components are typically contained within a resin enclosure, such as polycarbonate. Heat can only leave the components of the system via convection and as resins, such as polycarbonate, are more an insulator than conductor the heat transfer performance is poor. To overcome these drawbacks, some providers mount heat sinks in the resin enclosures, which add costs and can also invalidate airframe manufacturer rules, such as touch temperatures shall not exceed 50°C. In addition some rules exist that insist on metallic enclosures being ground bonded, which usually is a large screw with an earth strap going to aircraft ground. Mounting the power supply assembly in the seat structure according to the present invention offers a number of benefits. First, the components of the power supply assembly are well protected from damage. The seat structure is typically formed from metal, such as aluminium or an aluminium alloy, which has much better heat transfer properties than resins, such as polycarbonate, both in terms of convection and conduction. Further, the electronics can be seamlessly integrated into the seat assembly, not only improving the appearance and reliability but maximising passenger space. A seat assembly for a passenger vehicle, such as an aircraft, typically comprises a number of different components. One common arrangement of seat assembly comprises a frame or framework. The frame or framework typically comprises one or more spars extending generally horizontally from side to side of the seat, for example a front spar and a rear spar. It is common to provide legs or leg assemblies extending downwards from one or more spars of the seat assembly. Spreaders extend from the one or more spars, for example between a front spar and a rear spar. The spreaders may also extend upwards, in particular from the rear of a spar or from the rearmost spar, to provide support for the seat back, an armrest or the like. In one embodiment, the power supply assembly of the present invention comprises an electrical power supply converter assembly, which functions to receive electrical power from the electrical system of the vehicle and convert the electrical power to a form suitable for providing to a PED. The electrical power supply converter assembly is mounted in or on a first member of the seat frame, preferably within the first member. The first member may be any suitable member of the seat frame. In one preferred embodiment, the first member is a spreader. In another preferred embodiment, the first member is a spar. In an alternative preferred embodiment, the first member is a leg of the seat assembly. In one embodiment, the power supply assembly of the present invention comprises an electrical connector assembly comprising one or more connectors or ports for connecting to the PED of the user. In one embodiment, the electrical connector assembly is mounted in or on a member of the seat frame. The electrical connector assembly may be mounted in or on the same member as the electrical power supply converter assembly, that is the first member. Alternatively, the electrical connector assembly may be mounted in or on a different member of the seat frame to the electrical power supply converter assembly, that is a second member, wherein the second member is different to the first member. The second member may be any suitable member of the seat frame. In one preferred embodiment, the second member is a spreader. In another preferred embodiment, the second member is a spar. In an alternative preferred embodiment, the second member is a leg of the seat assembly. In use, the PED of a passenger is connected to the electrical port of the electrical connector assembly. The electrical port or connector for connecting to the PED may comprise a USB connector. The USB connector may comprise connectors typically found within the commercial marketplace supported by Portable Electronic Devices. The connector may be of the form known as Universal Serial Bus (USB) substantially as defined by the USB Implementers Forum, Inc. (USB-IF). The connector may be that known as Type A. The connector may be that known as Type C or other successor designation. The electrical port or connector may be supported by an insulator to prevent short circuit with any metallic part of the structure in which the electrical connector is mounted. The insulator may be metallic suitably coated to prevent electrical continuity. For example, the insulator may be anodised aluminium. The insulator may be formed in such a way to substantially control the insertion of the mating plug into the electrical port or connector in order to facilitate a consistent insertion to reduce wear and tear to the vehicle mounted electrical connector. The insulator may be manufactured in a polymer, such as a resin. The polymer may be shaped to support the vehicle mounted port or connector both at its opening and at its mounting position. The polymer insulator may be manufactured using injection moulding techniques, 3D printing techniques, machined from solid or formed under vacuum. The insulator may comprise at least a portion that allows light to be transmitted therethrough from the power supply assembly. For example, the insulator may be formed partly or wholly of a translucent material. This provides a structure, such as an illuminated annulus, to provide a light, for example to help the passenger locate the electrical port or connector. The illumination may be used to identify the location the electric port or connector. The illumination may also signify the status of the connector such as ready to use, in-use or not available. The status may be shown via colour, by intermittent pulsing of the illumination or via a combination of both. The illumination may also be configured to reflect carrier brand identities. The electrical port or connector may be arranged to be mounted upon a printed circuit board (PCB), which is comprised in the electrical connector assembly. Where a plurality of electrical ports or connectors is provided within a single location the electrical connectors may be preferably arranged on a single printed circuit board (PCB). The printed circuit board (PCB) may be configured to receive electrical power and control circuits from an external source. The printed circuit board (PCB) may also house illuminating devices such as one or more LEDs, for example to provide the illumination fo the ports or connectors indicated hereinbefore. The electrical connector assembly preferably comprises an electrical power converter assembly. The electrical power converter assembly may be any electricity delivery control device known in the art as a charge port controller (CPC). A CPC may be provided for each electrical port or connector. Alternatively, a single CPC may provide electrical power to a plurality of ports or connectors and, hence, to a plurality of PEDs. The CPC shall interface with the PED being attached via the consumers cable and plug assembly to determine the amount of power to be transmitted to the PED. The CPC may be configured to be on a discrete PCB assembly and not on the electrical connector assembly. The separate and distinct PCB assembly may be referred to as a mother board while the electrical connector assembly may be referred to as a daughter board. The daughter board assembly may connect to the mother board using a cable or wire assembly. The wire assembly may be permanently connected to each discrete board assembly. The wire assembly may comprise a permanent connection at one end, for example solder terminals to the board and a wire-to- board connector known in the art at the other end. The wire assembly may also be provided with wire-to-board connectors at both ends. The daughter board may be preferably produced with a board-to-board connector know in the art to interface with and connect to a mating board-to-board connector mounted on the mother board. The disposition of the board-to-board connectors may be configured to provide a polarised connection between the mother board and daughter board in order to avoid false connections. The mother board may be preferably configured to receive in-coming power from the vehicle power supply. The incoming power may be transformed if necessary to the appropriate power configuration required by PEDs. Incoming power may preferably be 28VDC; incoming power may be 110VAC. Typically PEDs are arranged to operate on a 5VDC, 2A supply, variants of which conform to the USB-IF USB specification or successor specification. Incoming power may be transformed by a separate device located in a convenient location for distribution to the daughter board outlets. Transformation may be performed by the daughter board or preferably on the mother board. The mother board may be configured to allow heat generated by the transformation of power to be transmitted by convection to the surrounding airflow. It may be, more preferably, configured to allow heat to be transmitted directly by conduction. One or both of the mother board and daughter board assemblies may be preferably arranged to mount within the structural framework of the seat. Heat generated as a by-product of power transformation or by delivery to the PED may be transferred to the structural framework of the seat directly from the mother board and/or the daughter board, or through a mounting frame or member of the mother board and/or daughter board assembly. The framework comprising the passenger vehicle seat structure is typically manufactured using a metallic material. The framework may comprise a number of interconnected elements, as described hereinbefore. The framework may provide channels to provide a conduit for any cabling that may be required to furnish power to the power outlet. The framework may also be produced with holes to guide the cabling from one side of the framework to the opposite side of the framework. The framework may provide within its structure pockets to locate and secure the electronic assemblies such that the power infrastructure can be installed at a date other than the original installation date without the need for further regulatory approvals. Furthermore these pockets may be extended through the structure or they may provide a series of interconnected galleries. The pockets provided in the framework may be produced with holes to facilitate the simple assembly and disassembly of the power components. The power components may be assembled directly onto the framework to facilitate a mechanical transfer of heat from the power components to the framework. The mechanical assembly of the power components to the framework may also be used to provide a ground in the electrical sense. Heat may be dissipated by conduction from the heat source to the framework and then via convection from the framework to the surrounding environment. The framework may be considered as a heatsink redirecting heat from a hot device such as the mother board by increasing the surface area in free air and hence cause a cooling effect. The framework may be manufactured from an alloy principally containing aluminium to provide the requisite cost/weight ratio required for passenger vehicle seat structures. The seat framework may be finished in a decorative material to prevent corrosion and enhance the frameworks appearance. The decorative finish may be caused by an electromechanical process known as anodising in the art. The decorative finish may be mechanically applied. The decorative coating may be electrolytically applied. The decorative coating may be an electrical insulator. The coating of the coated framework may provide an effective shield for emissions radiated from the electronic components during power transformation. The coating may be selectively removed to allow the electronic assemblies to benefit from an external ground. The framework may provide the enclosure for the electronic components such as the mother board and the daughter board. The framework may have an aperture created to permit the daughter board to be easily removed and replaced within the framework. The framework may be provided with a cover to hold the daughter board in place during use. In particular, the daughter board may be housed in an open cavity or void formed in a member of the framework, with the cover closing the open cavity or void. The cover may be manufactured in a polymer material finished to reflect the interior design or brand characteristics of the passenger vehicle. The cover may be manufactured using injection moulded techniques. The cover may be 3D printed. The cover may be produced using a casting process. The cover may be manufactured in the same material as the seat framework. The cover may be preferably manufactured from a metallic substance. The cover may be selectively finished in order that it provides electrical continuity with the seat framework. The seat framework may be selectively finished to enable the electrical continuity with the cover. The cover may preferably permit the replacement of the daughter board without removing the mother board. The cover may secured using one or more screws. The cover may be secured suing a screw operated cam. The cover may be configured with one or more apertures to reflect the configuration of the daughter board. The cover may be a replaceable item to facilitate changes to the connector configuration of the daughter board. The cover may be provided without apertures to permit future upgrades to the seat based power system. The cover may be provided without apertures to support deletion of the power supply system from the seat assembly without having recourse to recertification of the seats. The cover may be considered a non-structural part of the seat framework. The cover may comprise a plurality of cover portions assembled to the framework by clips. The cover may be assembled to the framework using screws. The cover may be permanently attached to the framework using adhesives or by welding. Similarly, the framework may be provided with a cover to hold the mother board in place during use. In particular, the mother board may be housed in an open cavity or void formed in a member of the framework, with the cover closing the open cavity or void. In a further aspect, the present invention provides a vehicle comprising a seat assembly as hereinbefore described. The vehicle is preferably a passenger vehicle. Such vehicles include motorized vehicles, such as cars, vans and buses, water borne vehicles, such as ferries and cruise ships, and air borne craft, such as passenger aircraft. The seat assembly is particularly advantageous when installed in a passenger aircraft. A seat assembly in the vehicle may accommodate one or more passengers, with the or each passenger having their own seat. A power supply assembly according to the present invention may be provided for each seat, such that each passenger has their own power supply assembly. Each seat may be provided with a single electrical port or connector, such as a USB port, or a plurality of ports or connectors for the passenger seated in the seat. Alternatively, a single power supply assembly may provide power through a plurality of electrical ports or connectors, such as USB ports, to a plurality of seats, for example all the seats in a multi-seat assembly. Again, each seat may be provided with a single electrical port or connector, such as a USB port, or a plurality of ports or connectors for the passenger seated in the seat. Embodiments of the present invention will now be described, by way of example only, having reference to the accompanying drawings, in which: Figure 1 is a perspective view of a typical seat assembly for a passenger vehicle; Figure 2 is an end view of the seat assembly of Figure 1; Figure 3 is a cross-sectional view of one embodiment of the power supply assembly of the present invention located in the spreader of a seat assembly; Figure 4 is a partial cross-sectional view of the spreader of the embodiment of Figure 3; Figure 5 is a diagrammatical view of components of the power supply assembly of a second embodiment of the present invention; Figure 6 is cross-sectional end view of the components of the assembly of Figure 5; Figure 7 is a diagrammatical representation of a power supply assembly of one embodiment of the present invention showing components of the assembly outside of a seat assembly; Figure 8 is a diagrammatical representation of a power supply assembly of a further embodiment of the present invention showing components of the assembly outside of a seat assembly; Figure 9 is a cross-sectional view of a further embodiment of the power supply assembly of the present invention located in the spreader of a seat assembly; and Figure 10 is a partial cross-sectional view of the spreader of the embodiment of Figure 9. Turning first to Figures 1 and 2, there is shown a seat assembly, generally indicated as 2. The seat assembly 2 is typical of a seat assembly installed in passenger vehicles, in particular aircraft. The seat assembly 2 comprises a generally horizontal front spar tube 4 and a generally horizontal rear spar tube 6, extending parallel to each other along the length of the seat assembly. Front legs 8 extend downwards from the front spar tube 4. Similarly, rear legs 10 extend downwards from the rear spar tube 6. A seat spreader 12 extends between and connects the front and rear spar tubes 4, 6 and comprises a first spreader portion 12a extending between the spar tubes 4, 6 and a second spreader portion 12b extending upwards from the rear spar tube 6. A seat arm 14 is connected, typically pivotally, to the upper end of the second spreader portion 12b, in known manner. The components of the seat assembly 2 shown in Figures 1 and 2 are typically formed from metal, more typically a light metal, such as aluminium or an alloy thereof. The seat assembly shown in Figure 1 provides seating for three passengers. It will be appreciated that a seat assembly for accommodating fewer passengers or more passengers may be constructed in an analogous manner to that shown and described above. Turning to Figures 3 and 4, there is shown a power supply assembly according to one embodiment of the present invention. The power supply assembly is shown mounted in the spreader of a seat assembly. The power supply assembly may be mounted in a spar or a leg of the seat assembly in an analogous manner to that shown in Figures 3 and 4. References to a ‘spreader’ are therefore to be understood to include references to a spar or a leg in like manner. The power supply assembly, generally indicated as 102, is mounted in a spreader 104. The spreader is provided with a first void 106 to accommodate the assembly 102. The first void 106 is preferably sized to accommodate the assembly 102 and provide free space around the assembly within the spreader 104. This allows for free air to surround the assembly 102, for example to assist in cooling the assembly 102. A pocket 108 is provided in the spreader 104 opening into the first void 106 to house components of the assembly 102, as described hereinafter. A second void 110 is formed on the opposing side of the spreader 104 for housing components of the assembly 102, as described hereinafter. The second void 110 communicates with the first void 106 via the pocket 108, as shown in Figure 3. The power supply assembly 102 comprises a converter printed circuit board (PCB) assembly 120. As shown in Figure 3, the converter PCB assembly 120 is mounted within the void 106 and connected to the spreader 104 by screws 122. A PCB-to-PCB connector 124 extends through the pocket 108 and comprises a first connector part mounted to the converter PCB assembly 120 and a second connector part located in the second void 110. The converter PCB assembly 120 is connected to the electrical power system of the vehicle by a cable 126. First and second power connections, in particular USB ports 130a and 130b are provided in the second void 110 and are connected to the converter PCB assembly 120 by the PCB-to-PCB connector 124. An insulator 132 is provided around and/or between the USB ports 130a and 130b and provides support to the ports. A cover plate 134 is provided around the openings of the USB ports 130a and 130b. In use, a passenger connects their PED by plugging a suitable USB plug into one of the USB ports 130a, 130b. Electrical power is drawn from the electrical system of the vehicle, converted into a voltage appropriate for supply to the PED by the converter PCB assembly 120, and supplied to the USB ports 130a, 130b via the PCB-to-PCB connector 124. Heat generated by the operation of the components, in particular the converter PCB assembly 120, is lost to the air in the first void 106 and, more significantly, to the spreader 104. In this way, the spreader 104 acts as a heat sink for heat generated by the converter PCB assembly 120. Turning to Figures 5 and 6 there is shown an alternative embodiment of the power supply assembly of the present invention. The power supply assembly, generally indicated as 202, comprises a power converter PCB assembly 204 mounted within the hollow interior of a spar 206 of a seat assembly. The spar 206 may be the front spar or the rear spar. Cables 208 connect the converter PCB assembly 204 to the electrical system of the vehicle and to one or more power outlets, such as USB ports, for supplying electrical power to the PED of a passenger. The power outlets are located remotely from the converter PCB assembly 204, for example in a spreader of the seat assembly, as shown in Figures 3 and 4 and described hereinbefore. As shown in Figure 6, the inner wall of the spar 206 is provided with opposing support members 210, each provided with a slot 212. The converter PCB assembly 204 is mounted within the spar 206 by having opposing edge portions engaged in the slots 212. The location of the converter PCB assembly 204 within the spar 206 allows heat generated by the operation of the converter PCB assembly 204 to be dissipated both to the air within the hollow spar 206 and by conduction to the material of the spar itself. Turning to Figure 7, there is a shown a diagrammatical representation of the components of a power supply assembly of one embodiment of the present invention outside of the seat assembly. The power supply assembly, generally indicated as 302, comprises a power converter PCB assembly 304. The converter PCB assembly 304 comprises a connector 306, for connecting to the electrical system of the vehicle. Cables 308 extend from the converter PCB assembly 304 and connect the converter PCB assembly 304 to a connector port assembly 320. The connector port assembly 320 comprises a connector PCB assembly 322 and one or more connector ports, for example one or more USB ports 324. The power supply assembly 302 of Figure 7 is appropriate where the converter PCB assembly 304 is located in the seat assembly some distance from the connector port assembly 320. The assembly 302 finds use, for example, in the embodiment shown in Figures 5 and 6. Turning to Figure 8, there is a shown a diagrammatical representation of the components of a power supply assembly of a further embodiment of the present invention outside of the seat assembly. The power supply assembly, generally indicated as 402, comprises a power converter PCB assembly 404. The converter PCB assembly 404 comprises a connector 406, for connecting to the electrical system of the vehicle. A PCB-to- PCB connector 410 connects the converter PCB assembly 404 to a connector port assembly 420 and comprises a first connector 410a mounted to the converter PCB assembly 404 and a second connector 410b mounted to the connector port assembly 420. The connector port assembly 420 comprises a connector PCB assembly 422 and one or more connector ports, for example one or more USB ports 424. The power supply assembly 402 of Figure 8 is appropriate where the converter PCB assembly 404 is located in the seat assembly close to or adjacent the connector port assembly 420. The assembly 402 finds use, for example, in the embodiment shown in Figures 3 and 4. Turning to Figures 9 and 10, there is shown a power supply assembly according to one embodiment of the present invention. The power supply assembly is shown mounted in the spreader of a seat assembly. The power supply assembly may be mounted in a spar or a leg of the seat assembly in an analogous manner to that shown in Figures 9 and 10. References to a ‘spreader’ are therefore to be understood to include references to a spar or a leg in like manner. The power supply assembly, generally indicated as 502, is mounted in a spreader 504. The spreader is provided with a first void 506 to accommodate the assembly 502. The first void 506 is preferably sized to accommodate the assembly 502 and provide free space around the assembly within the spreader 504. This allows for free air to surround the assembly 502, for example to assist in cooling the assembly 502. A pocket 508 is provided in the spreader 504 opening into the first void 506 to house components of the assembly 502, as described hereinafter. A second void 510 is formed on the opposing side of the spreader 504 for housing components of the assembly 502, as described hereinafter. The second void 510 communicates with the first void 506 via the pocket 508, as shown in Figure 10. The power supply assembly 502 comprises a converter printed circuit board (PCB) assembly 520. As shown in Figure 9, the converter PCB assembly 520 is mounted within the void 506 and connected to the spreader 504 by screws 522. A PCB-to-PCB connector 524 extends through the pocket 508 and comprises a first connector part mounted to the converter PCB assembly 520 and a second connector part located in the second void 510. The converter PCB assembly 520 is connected to the electrical power system of the vehicle by a cable 526. First and second power connections, in particular USB ports 530a and 530b are provided in the second void 510 and are connected to the converter PCB assembly 520 by the PCB-to-PCB connector 524. An insulator 532 is provided around and/or between the USB ports 530a and 530b and provides support to the ports. A cover plate 534 is provided around the openings of the USB ports 530a and 530b. The first void 506 is provided with a cover 540. Posts 542 extend from the cover 540 to the converter PCB assembly, allowing the screws 522 to retain both the cover 540 and the converter PCB assembly 520. In use, a passenger connects their PED by plugging a suitable USB plug into one of the USB ports 530a, 530b. Electrical power is drawn from the electrical system of the vehicle, converted into a voltage appropriate for supply to the PED by the converter PCB assembly 520, and supplied to the USB ports 530a, 530b via the PCB-to-PCB connector 524. Heat generated by the operation of the components, in particular the converter PCB assembly 520, is lost to the air in the first void 506 and, more significantly, to the spreader 504. In this way, the spreader 504 acts as a heat sink for heat generated by the converter PCB assembly 520. The embodiment shown in Figures 9 and 10 is particularly advantageous for location at positions on the seat assembly that are more readily accessible by passengers, with the cover 540 preventing access to the components of the power supply assembly 520.