Well the process is quite simple really - you see a (very) cheap set of R8 Brembo 4-pots and 362mm APR 2-piece rotors on pistonheads, the kind people at asn essentially peer-pressure you into buying them, and then you find out the caliper carriers are for a Passat hub and won't fit an S3.
You then trawl the internet for about 3 months before N8 comes along and says he knows a guy, a VAG/Brembo guru, a man named Dave. N8 puts you in touch with Dave, and Dave then agrees to build you a set of one-off custom carriers for the brakes. You manage to miss each other constantly for about 3 weeks, but eventually you're both at home at the same time so you can finally pay Dave for the carriers and they get sent out that day. The following week you have to go to London so can't pick your car up from the bodyshop until the following weekend. You call your local mod guy/garage and he says he can squeeze you in on Tuesday. You go pick up the car and find that not only do the brakes stop you on a pin-head, but they also have a BETTER feel than the standard set up. You be very happy you joined asn and then upload a bunch of pictures so people can share in your joy. Then you pour yourslef a beer and go sit in the garden because even though it's only about 10degrees, the sun is out, and that's enough in Aberdeen.
Or, in other words, R8 calipers + AP Racing discs + DaveB carriers =
The way they were:
The parts needed:
And, the finished product. Now with (temporary) 4mm spacers (=ET44 8.5J) and no rubbing.
Massive thanks to N8 and of course Dave (Brown). We got there in the end!