Thanks for the fast reply Steve,
Do you have any links you could send to me for YouTube videos on where I can start with this. I'll have a crack at this with my Dad, who's a mechanic, when we get a chance.
The timing of this couldn't be any worse as I'm looking to trade my car in!
I wonder what Audi would charge to fix this? They were charging £160 just for an investigation, so I said I'll get the codes etc before I even consider paying £160 for plugging the car in to read some codes.