Have you been under the dash recently, when i had an alarm fitted, they disturbed a wire and i had the same problem.
However it really won't work now as I can see that the contact onto the rear screen has sheared off, so it really won't work.
Thanks for that. There was an alarm fitted but I have just removed it. The heated window has never worked since I bought the car. There most be some sort of 'brain' for it because the switch is not an on/off type. Any more info?