Dose the filter have a big set of flats on the end?
The one on our Lupo does, and that handily fits the huuuuge socket I bought for getting the (non-cannister) filter off my A3. It means you can get a ratchet on it. Some decent filters (Mann/Bosch) have a handy hex end you can get a spanner on.
I remember cursing the spanish bastard that factory-fitted the filter on my ibiza- that look a lot of swearing to shift.