And I have found the answer!.
For anyone who may be interested...
There is a small plastic filter in the drain pump underneath the unit. It has a large outlet, and a small inlet, and was full of sludge.
To get to it you need to take the kicker plate off the bottom, undo the screws on the front of the plate to get access to the pump motor etc. The clear plastic container is at the front.
It unplugs from the pump and has another small hose which is easliy removed.
Once cleaned, the machine works like new.
Woohoo!.
Adrian
February 2008