Rear Mk5 GTi brake calipers onto 8P1 TDi?

[munchkincoupe]

Need a quick reply please as I've got a breakers waiting for me to buy a full set from them:

Are the rear brake calipers from a Mk5 Golf GTi an upgrade over the calipers already on my 04 2.0TDi A3 8P1?

If so are they also a direct fit and do they need larger discs and different pads too?

Thanks for your help with this