Darryl...
I've got the same problem in 1996 300 Tdi.....
I've traced the wiring all the way to the Electrci Window ECU (why they need one is beyond me, but hey....) It sits on the side (Left hand as you look at it) of the ABS ECU behind the glove box.
I traced my fault to a loose connection on the white wire which sends out power to the cut-out switch in the centre console which is then sent to the motors/switches. I 'tightened the connector and the problem went away for a month or so..... but now its back - may be an internal fault in the ECU - am due to investigate further this week so will let you know how I get on........
Bri
:beer:
AHHHHHHHH....
Just seen whre on the rock you are...
It may not be in the same place on yours as its all going to be back-to-front (or do you drive on the imperially decided correct side of the road over there

)