cheers colin..just saved me a small fortune..but mine was the pump just a little clogged with fluff...to add to colins, you have to remove the top lid (two screws at the back and slide the whole top piece towards the back to release) then take the side of by the water collector (one screw on the top, about four or five on the back and then slide the whole thing directly backwards to release) then look into the side at the bottom, you will see where the two plastic clips which hold the pump mechanism on the back of the dryer, push these in with a screwdriver and simultaneously pull back on the plastic box at the back of the washer and with a harsh pull it will come off. Then I cleaned round the pump part and dipped it in clean water until it was pumping water into the tray again. The lower tray was full of fluff which had clogged the entrance for the pump, but colins answer above would have the same effect so check that the polystrene level is moving easily.
Jonny walker, January 2009