I was also charged £310 from Audi Glasgow for a standard service. When I checked what they had done they only checked everything and after 45k miles you would expect them to change the oil and plugs. To my horror the plugs were still the original.
I have learned from this site that to please fleet managers Audi boast 18k service intervals by using "long life" oil and plugs but what they don't tell you is if you have for example a 2.0 T petrol engine the long life oil certainly shortens the life of your engine by creating sludge which damages the oil flow round the engine...
After reading a few posts on the subject I drained the "long life" oil and it was like treacle and the plugs just disintigrated in my hand.
I now change oil and plugs every 6k using Edge and engine is now much happier... Rule of thumb, if the stealer tells you anything, assume they're wrong and just want to rip you a new mortgage, take it to a specialist instead.