Unfortunately they found that there was a crack in my spare wheel! Odd because whilst it has obviously been used it appears to be in pretty good condition.
Very strange. I must say that I (fortunately!) haven't had to use the spare, but I am surprised that nobody has noticed this before in the 3 years I have had the car (bit embarassing really.....).
Or has some smart chap swapped the wheel over. Apart from servicing etc I lost the car for a week after it had all 4 wheels stolen and had to have a new bumper last year after someone ran in the back of me (court case next week!).
New wheel is £330 (inc VAT) from Audi or £190 or so (+VAT) from VAGparts.
When I get my coilovers fitted and finally sort out the ABS controller, with recent regular servicing, tax, MOT and tyres (4xPS2s
), plus some paint after a rather too close encounter with a gateway in Devon ( 
not such a cheap holiday after all), I will have spent the best part of £3K on the damn thing in the last 2 months, so if anyone has a spare 17" Avus wheel that they don't need I would be interested. It doesn't have to be pristine, but not too bad. Most of what I have seen on Ebay are sets of 4.
David