Most on the time, they will fit but you will need to buy ne carriers (things that hold the carriers)
If you get S3, R32, 3.2 V6 calipers, they will go straight on (like mine) - need to ensure you have new sheilds, pipes, pads, discs, clip that holds the pads tight.
or change your carriers to 312mm ones off the GTI, add 312 discs and pads and you have a 312mm set up (like i have on the rear of mine - not fitted yet)