I had exactly the same problem. Rang the phone number given, ordered the part (now £47), received it 3 days later. Very, very easy to fit, and only two plug connections, simple. DW now working fantastic well.
Tom Jenkins, March 2007
Mine has stopped as well, the catch is operated by a solenoid, to access this you need to remove your door - Switch off and isolate from the electricity(held on by a spring catch each side and 2- screw internally) your manual tells you how to remopve the door, then remove the white panel (there are 3-screws each side of the door and you need a special screw driver - readilly available from most good diy shops)
You will see the solenoid on the front of the door removasl is easy it is held in place with one screw and two push on connectors.
Hygena Extracare (08457 959722) only sell the complete soap dispenser hopefully the solenoid is on that, they do not seem to be able to advise this. Part Number is 37021 cost (incl dely and vat) £40.31