thing is the disks and pads he has are relatively new and they just cannot stop it from 140+ leptons 
and i cant see 312 being much better or are they?? i take it that all he needs for the 312mm swap is the carriers and disks as the caliper is the same??
Then he bought sh!t disc and pads and must have sh!t tyres!
A vr6 has this setup and does 140mph all day everyday.
Buy good grooved disc's buy good pads that need to be hot to work and go spend £100 a corner on good tyres.
hes only just bough the car and hes done nothing to it, nice too see you guys actually read the op 
and as for the tyres yeh i have to agree with you toyo proxies are shyte 
I read he recently bought the car. This could be months ago!
I read the brakes are new, thinking that he bought them!
I read that you want a cheap alternative to the expensive brembo caliper up grade.
I read that you think these brakes are crap, knowing that with good pads, disc's and tyres they are fine on a track car that is using the brakes heavily for long periods of time.
Toyo proxies. Cheap and good for the money.
Toyo proxies fitted to a 1.8t mk3 with at least 225bhp are not up to the job!
I said £100 a corner not £40!
Then after you done that buy some braided brake lines and bleed with some 5.1 fluid.
