My A3 is due it's first service under my ownership and I am wondering whether it's supposed to be the major service or the interim service? What's the difference? Going to Audi Chingford to carry out the job. I will also be changing the cambelt & water pump there on the same day. Anyone had any experience with Chingford Audi? Thanks. By the way it's an '04 plate with 45k miles.