what size are the rear gti/ed30 set ups?
Could be wrong but are they 312mil 
Rears are 286mm, standard fronts are 312mm

So by the looks of things the rears are the same on the cupra as the GTI/ED30

I am very temped by the front brake upgrade, but will probably wait until I at least need to replace the front pads and then convince SWMBO that pads are very expensive
