Had my 21 plate Q7 down tools with the same error as many of you have experienced.
Dealing with the garage was as a bit of a pain, nothing was written down and no one wanted to place any blame on the part.
However, I picked the car back up today with a new alternator and battery at zero cost to me from Stratford Audi.
Now to follow up with Audi UK for recovery costs.
Thanks for all the advice on this thread, helped a lot in saving me a significant bill.