i just fixed ours this morning with the same fault. (also i looked on this site too for answers which there seems to be none)
TO FIX IT CHECK THIS FIRST/. check and unblock drain plug at bottom right front of your washer, behind the small panel.
If that was mega gunged up, clean a and re-try. if still not ok, check the small thin(ish) rubber hose running from the pressure switch (which is at the top on the inside of the washer) connects to a white plastic pressure bottle (looks like a fat syringe with a rubber hose at the bottom end of it). take the thin rubber hose off using pliers on the 2 clips each end (its about 20cm long)and test it for puncture holes. (ours had very tiny hole which i fixed with lots of electrical tape). THIS IS THE MAIN CAUSE OF OVERFILLING I HAVE BEEN TOLD! if puntured, fix and re-test.
if this is ok then connect that pipe back at the pressure switch end only and blow gently into the other end. the switch should make a clicking noise. if it doesnt, it needs replacing. too. DO NOT MESS WITH THE SCREWS ON THE PRESSURE SWITCH THEY ARE PRE SET AND I KNACKERED MINE BY TWISTING THEM. new pressure switch is only around a tenner from spareparts website takes about 8 working days though.
hope this helps and saves you money.
www.ringbilly.com my proper work site
billy
April 2007