For pads, i'd say just take it down to Kwik Fit since they have the free pads for life offer so you buy pads once, about the same price from audi if not cheaper, and they replace them for free every time they wear out. There are other aftermarket options for pads and discs but I haven't tried any. Unless you go for higher performance pads and disc I don't think there is much difference between different suppliers as there is strict regulation in the EU on safety components such as discs and pads.