Booked the car in today, the parts are no longer on back-order (there are eight sets in the country), my dealer has done about 30 replacements, so it looks like a widespread problem.
While I was there I got them to stamp my service book for the two major services so far; somehow they had forgotten to do this at the time. They also did this with my Wife's Polo.
Overall I'm not over the moon with the dealer service I have received (the Polo went in 7 times for a loud "clonk" on the front suspension, which is still there despite many parts being changed under warranty).
My next car? Are AUDI any better, or do they just cost more? Had a look at an A3 Cabrio today- it looked very nice but is it just the same box of bits underneath?