Instead of going for the 2.5 kit can't you go for the stage 2 kit and keep a low boost situation, which means you won't need to go for the cossie cams or inlet...

you could then go for a 300mm set-up or keep an eye out for a set of bigger second hand brakes... or even go for Foci RS mk1 brakes

the clutch STASON just sold was a good buy at half the price i think

Polybushes could be done a step at a time, and wasn't kaxe using the IB5+ box just with an LSD.

obviously the situation above is as if you are going for max power. but if you drop the power you could save some money. then you can go looking for more in the future and perform extra upgrades then