If you look at your option sticker in the spare tyre well (or handbook)
The front brake codes are like 1KL, 1LL and similar and the rear 1KW and similar. If you then look at the extra information on ECP site these codes are on there, but ECP are quite expensive compared to
ebay's premier-factors.
I always get the Audi and Mintex (or whatever) part numbers and then search on ebay and google for the part number to find the best price as they vary wildly.