If its PCH it HAS to be a franchised dealer. It's written in the contract you signed:
Section 9.4.1 "You agree to make sure that the Vehicle is serviced and maintained strictly in line with the manufacturer’s recommendations and that scheduled servicing and necessary maintenance is carried out only by authorised Audi dealers"
Best way is go to a specialist within 15 miles of the main stealer, get a written quote and ask the stealer to price-match. They usually do. Then go back to the specialist and give a tenner of the £200 you've just saved for his/her trouble