FIELD OF THE INVENTION This invention relates to apparatus for use in the digital printing of textiles. More specifically this invention relates to apparatus for continuous pre-treatment and also washing of fabrics prior to and after digital printing of textiles. BACKGROUND OF THE INVENTION Digital printing is a form of printing where micro-sized droplets of dye are placed onto the desired substrate through an inkjet printhead. Digital printing of textiles involves a four step process. The textile substrate has to be coated with pre-treatment solution or composition before it can be printed. This is because not all the chemicals that are mixed into the printing ink during the actual printing process can be passed through the piezo inkjet printheads without damaging them. These chemicals are pre-applied on to the textile substrate using a coating machine. Once the textile substrate has been pre- treated, it is ready to be printed by a digital textile printing machine. After printing, the textile is steamed in a steaming machine, during the course of which reactions occur between the chemicals applied to the textile substrate in the coating machine and the inks applied during printing in the digital printing machine. This also results in the printing ink being set into the textile. The final step in the process involves washing the printed textile. This results in excess ink and residual pre-treatment solutions or compositions being washed off the textile. Digital printing of textiles requires preferably small compact apparatus to allow chemical pre-treatment of printed fabrics by chemicals and, after printing, removal of those chemicals and excess inks or dyes. The apparatus must be able to process either very short lengths of fabrics or long lengths of fabrics in a continuous process. Generally digital printing is used on short lengths of textiles although as printing speeds increase longer runs can be envisaged. US Patent No. 4,373,362 describes a washing apparatus for textiles printed by conventional printing. The apparatus described in that specification is a large machine not suitable for digital printing. This is because digital printing uses small amounts of dyes. Also the machine is not adapted to handle short pieces of textiles as it is designed for high production output. US Patent No.' 5,497,637 relates to apparatus for textile dyeing processes. It requires a large amount of water as well as space. GB Patent No. 800,926 relates to a process for moisturising fabric to achieve uniform moisture content and apparatus therefor. None of these specifications disclose the concept of combining the functions of washing and coating fabrics or textiles. Additionally, it has been found that it is very difficult to wash off excess reactive dyes and acid dyes after fixation with conventional washing apparatus. SUMMARY OF THE INVENTION According to one aspect of this invention there is provided an apparatus for conducting coating and/or pre-treatment of textiles prior to digital or other printing of those textiles and also washing of those textiles after printing, said apparatus including a textile supply unit for delivering textile to said apparatus; a chamber for holding a washing composition; drive means operable in conjunction with guide means for passing textile through said chamber so that it is in contact with washing composition in said chamber; means for removing excess washing composition and residual dyes or inks from washed textile following its passage through said chamber; a bath for holding a coating or pre-treatment composition; drive means in conjunction with guide means for passing textile through said bath so that it is in contact with coating or pre-treatment composition in said bath; and means for removing excess coating or pre-treatment composition from coated textile following its passage through said bath. Usually the textile which is passed through said chamber has been printed and carries with it excess printing inks or dyes and coating or pre- treatment chemicals. Preferably said chamber is a U-shaped chamber containing at least one heating element to keep the temperature of the washing or pre-treatment composition within preferred ranges and under control by means of a temperature controller. The preferred temperature ranges of the compositions lie within the range 0-90°C and those preferred temperature ranges can be selected according to the type of composition concerned. The washing composition preferably is water-based. Water supply to the chamber preferably is regulated by a level switch. Washing chemicals preferably are supplied automatically on demand by a peristaltic pump. Circulation of the washing composition in said chamber preferably is provided by a mixing pump which also has the effect of maintaining a relatively constant water temperature throughout the washing composition. Preferably a set of rollers is provided within the chamber to guide the textile through the chamber and maintain it in contact with said washing composition. More preferably said set of rollers is movable relative to the chamber to assist in feeding the textile around the set of rollers prior to operation of the apparatus. The set of rollers may constitute part of the guide means which act in conjunction with drive means for passing the textile through said chamber. The drive means for passing textile through said chamber preferably includes a set of two rollers covered by rubbers of different hardness, with the bottom roller being driven and the top roller being operated by regulated pressure to squeeze said textile. In addition to providing motive force to the said textile, the set of rollers act to remove excess water and washing chemicals. Preferably the means for removing excess washing composition and residual dyes or inks from said textile also includes one or more high frequency water spray nozzles. The high frequency water spray nozzles spray pressurised water on to the textile. The high frequency nozzles are connected to water- containing chambers and a pressurised gas, preferably air, is forced into the water-containing chambers to expel pressurised water through the high frequency nozzles. The nozzle apparatus includes high frequency air switching solenoid valves capable of switching frequency in milliseconds combined with conventional water valves. The object is to achieve a higher effect but minimising water consumption. The pressurised water removes chemicals or residual inks from textiles. Preferably the textile, after passing the high frequency water/air nozzles passes through another set of squeezing rollers to remove any further remaining excess moisture from the fabric. In an alterative configuration, textile (usually prior to printing) is not passed through said chamber but is instead passed through a bath holding a coating composition. The level of coating composition is controlled by a level switch and filling of the bath is carried out by a peristaltic pump. In both operations the textile preferably then passes into a dryer, preferably an infrared dryer, for drying and after that is wound into rolls on a winding device. However, gas heating or steam can be used to dry the textile. The apparatus preferably includes means for receiving textile after it has passed through the apparatus. The textile supply unit preferably includes support means for a spindle around which is wound the textile. Additional chambers for holding a washing composition can be provided to increase production output. The apparatus preferably is a standalone machine but is usually used in conjunction with a dryer. It can be used in conjunction with any printer using any type of printing head, and in conjunction with conventional printing processes. It is anticipated the apparatus could be used in conjunction with all types of dyes and textiles. DESCRIPTION OF PREFERRED EMBODIMENT In order that the invention may be more clearly understood a preferred embodiment is disclosed with reference to the accompanying schematic drawings in which: Figure 1 is a diagrammatic side view of an apparatus according to the present invention in washing mode; Figure 2 is a diagrammatic side view of the embodiment of Figure 1 in the coating or pre-treatment mode; Figure 3 is a diagrammatic side view of the apparatus of the preferred embodiment in washing mode in conjunction with a dryer and winding apparatus; Figure 4 is a diagrammatic side view of the apparatus of the preferred embodiment in coating or pre-treatment mode in conjunction with a dryer and winding apparatus; Figure 5 is a diagrammatic side view of a nozzle for use in the embodiment. In Figure 1 the numeral 10 generally identifies an apparatus according to the present invention. The apparatus includes textile delivery means 12 including a support 14 for a roll of textile 16. The textile (which has been subjected to a printing process) is unwound from the roll of textile 16 by the action of a first pair of squeeze rollers 18 and 20. Lower roller 18 is driven. The textile passes over tension bar 22 and into chamber 24 which contains washing composition maintained at a relative constant temperature by water heating element 26 and by agitation of the liquid content of the chamber by a pump or other means (not shown). Water supply to chamber 24 preferably is regulated by a level switch. Washing chemicals preferably are supplied automatically on demand by a peristaltic pump. The textile is guided through the chamber 24 by passing under and over a set of rollers 28. The set of rollers is movable relative to the chamber. This enables the textile to be placed in position around the rollers prior to immersion in chamber 24. After passing through chamber 24 the textile passes between squeeze rollers 18 and 20. The squeeze rollers are fitted with rubber facings of different hardnesses. The squeeze rollers, in addition to providing motive force for movement of the textile through the chamber, also squeeze out excess washing composition from the textile. Upper roller 20 is operated by regulated pressure to squeeze the textile according to the type of textile. The textile then passes under a dipping roller 30 and is exposed to high frequency pressurised water spray from high frequency spray nozzles one of which is shown and designated 32. This further removes excess washing compositions and from the textile. Subsequently the textile passes through a second pair of squeeze rollers 34 and 36 also provided with rubber facings of differing hardnesses and further excess washing composition and/or water is removed from the textile. Lower roller 34 is driven and upper roller 36 is operated by regulated pressure to squeeze the textile according to the type of textile. The textile then passes under a roller 38 to the next piece of apparatus in the process, which usually is a dryer 42 as shown in Figure 3. The drying chamber 44 is provided with an infrared dryer 46 and an exhaust fan 48 to remove heated air containing water vapour from drying chamber 44. The textile passes under and over a set of rollers 50 in the drying chamber 44 and then out of the dryer 42 to a winding machine 52. The winding machine winds the textile into a roll. The high frequency spray nozzle 32 as used in the embodiment shown in Figures 1 to 4 is described in more detail in Figure 5. The spray nozzle is provided with an inlet 60 through which water flows. The flow of water is controlled by water solenoid valve 61 and water check valve 62. The water after passing through the valves enters the air/water firing chamber 65. Pressurised air enters through pressurised air inlet 63. The flow of air is controlled by high frequency air valve 64. Pressurised air enters the firing chamber 65 in high frequency pulses (between 5 and 20 milliseconds). The effect of this is to shoot water through nozzle spray 66 onto the textile. At the time air enters the firing chamber 65, water check valve 62 is closed to halt the flow of water. This provides the water pulsation function. The effect is to create small droplets of water with high frequency and high speeds which clean the residual ink from the textile. Another effect is that there is a saving of water consumption because high pressurised water is not being used continuously but only intermittently. The nozzle is mounted within the chamber by use of mounting bracket 67. In Figure 2 the integers are as identified in Figure 1. However, in the coating or pre-treatment mode the textile bypasses chamber 24 and instead, when passing under the dipping roller 30, is immersed in coating or pre- treatment composition contained in tray 40. The level of coating composition in tray 40 is controlled by a level switch controlling a pump (not shown). It will be noted that first pair of squeeze rollers 18 and 20 are not in contact with the textile and are not therefore squeezing the textile. After the textile passes through the bath containing the coating or pre-treatment composition it passes between second pair of squeeze rollers 34 and 36. Excess coating composition is removed by those squeeze rollers. The textile then passes under roller 38 to the next piece of apparatus for use in the printing process, for example, as shown in Figure 4. It is believed that the present invention and many of its attendant advantages will be understood from the foregoing description and it will be apparent that various changes may be made in the form, construction and arrangement of the components of the present invention described without departing from the scope and spirit of the present invention or sacrificing all of its material advantages, the form hereinbefore described being merely a preferred embodiment hereof.