I had the same problem, and found a fix on a forum advising to replace the thermostats, did this today and I have a working dishwasher again. Parts from Partmaster, and around £17 for a pair of them inc. delivery
http://www.partmaster.co.uk/cgi-bin/product.pl?PID=927341&query=Proline%20PDW080%20thermostat&model=PDW080&path=67231,126608:262429,127537
Al, October 2010