I was considering a similar upgrade myself, but: for the bigger GTA calipers you would also need bigger/different rims (GTV wheels have not enough space) - besides the caliper is not the point. Floating discs are a good solution regarding weight and warping (but I guess good 330 one piece discs won't warp, I am now on Brembo sport discs 305 and they really work solid). O.k. but what about using these components in general on the roads - would this be legal in GB ? In Austria/Germania certainly not, there has to be an expertise that every single part is valid for the specific car type. Whitout this guarantee from the (parts)manufacturer not even a technical specialist can do a customized expertise. So in fact it would not be possible to bolt on 330 calipers without some kind of paper as they never were supplied for this model...(same for the discs)
Different case in GB ?