youll be fine
I have a set of 16" Bioline's that I used as winter wheels on the 08 Wolfsburg that I would like to put on the 12 GTI.
The Bioline's are 16X6.5 ET 50 and have 205/55/16 Dunlop Wintersports on them. The factory Detroits on the GTI are 18x7.5 ET 51.
I'm thinking clearance should be fine all the way around, wheel well wise, but I'm not 100% sure about the brakes.
Has anyone done this before?
Correct, 16in wheels are the minimum for those stock GTI brakes.