I've never paid Audi for any work on my cars. APS in Brackley have done all my servicing, upgrades and repair work. I've found, (like most specialists I suspect), that they're far more experienced in S and RS Audi's, and actually give a crap. Mainly because they're not underwritten by a multi-national corporation - they actually have to make money and this only happens if they're any good.
Hell, when I bought my car, the Audi service department told me there was no such thing as a 47i6 upgrade when I asked about the work that had been done on my car. (Despite the fact that the car has actually had the upgrade).
I trust Audi for exactly as long as their warranty is paying the bills, and not a second longer.