hi there
first thing is the 130bhp is a PD unit and has a 6 speed box. Also GT means you get pretty much all the features off the Petrol GTI model, so thats bigger alloys and sports seats. Not too sure about the suspension.
as far as brake discs go, discs all round (think they are 312mm front) with single pot calipers front and rear. The 150bhp diesel has lowered suspension, 6 speed box and recaro seats (well mine does).
hope this helps
have a nice day
sanj