Hi Richard first off, you have not stated what state it in other than not working?
1) when plugged in, and turned on does it make any sound whatsoever? If not check fuse in plug.
2) from the front look on the right hand side of the unit and see if the fan is turning if it isn't, (which seems to be one of the first issues on old units) see if it can be coaxed back into life by using a small screwdriver to flick the fan anticlockwise, if after a few goes it starts to show signs of turning on its own. Then do it a few more times eventually it will speed up and carry on and work until either you switch it off or the water bottle is full, where upon you have to start the fan or get a replacement fan (which is what I am after)
3) if the unit having been on for a few minutes is still not working you will need do switch off remove the case and check to ensure that the compressor is working there should have been a fridge like sound, and some of the pipes should be very cold to the touch, if not the fault could be that refrigerant has leaked out, or more checks are needed on the compressor. I hope something here might help a little.