Hi Claire,
Well isn't that strange? I've got the same problem, except that the filter light doesn't come on.
I stripped down the machine and found that the filter switch was faulty (open circuit). In the absence of a replacement I have shorted out the switch until I can get a new one (don't try this at home!).
So Claire, I suggest that you (or an engineer) check the filter switch. You will have to remove the bottom front cover to access it, by removing the cover over the condenser and then removing three screws. GOOD LUCK!
Peter Sorrell
May 2004