Thanks Gareth, my first port of call would have been the dealer, but they are 90 miles away from me! Not sure whether I can go to an alternative Audi dealership, presumably the warranty applies anywhere in the UK?
I have to say that the follow-up service from the (Audi) dealership I purchased from has been poor - they still owe me a second key which, despite numerous calls and emails, has yet to materialise. I'm therefore rather reluctant to go back to them at this stage.
Adam