i have focus rs brembos and std focus rs discs....on my s1.....what a nitemare it was tho,

the easiest conversion is the 2wd cossie disc and the 4x4 calliper, bolts straight on and NO messin whatsoever

you can use escos discs and 2wd callipers however you will need wheel spacers and spacers for the calliper to hub,

the other option in st170 discs and s2 callipers, fits nice just a little fettling going on tho....nothin major,

in fact you can use almost anything on anything now as ppl like reyland will take all your brakes and hubs and wheels and make em all fit together for about 130 quid