[tonupkid]

I don't get the problem here. Audi collect and return the car, or provide a loaner for free. Or is this just the dealers in the W Midlands?
I can't understand why you would pay for someone failing to fix what they were supposed to fix. I mean, where's the incentive for them to actually do that job if they can just **** about and then suggest, what is in effect wrecking your car to get bonnet open, once they are bored with messing around, or have another, more profitable, call to make.
The hit to fix it will almost certainly be less than the hit you'll take on your cars resale value with it unfixed.
I can understand your disillusionment, you've been taken advantage of. But have faith, not all dealers/mechanics are crooks. Ask around and take your car to whoever is trusted by the people you know.
Perhaps a little online research will point you to the solution.
Good luck with it and, far more important, good luck with the health issues.