Off the top of my head.....

APT Spec GT2871R Turbo with custom Actuator - £800 ish - £160 labour (plus gaskets)
FMIC and Small battery - £380 - £200 labour
Nismo 740cc Injectors - £360 - £50 labour
Apexi PowerFC - £500 ish (They are hard to get at the moment) - £400 labour (fit and map)
Stainless Exhaust - £300 ish (Depending on which one) - £50 labour
Front pipe and Elbow - £200 ish - Labour included with Turbo replacement
Air Filter - £100 ish (again, depending on which one)
Apexi AVC-R - £280 - £100 labour

Metal Head Gasket is a very good idea - £185 for Trust 1.8mm - £400 labour

That spec WOULD do 350bhp, maybe more and is a fantastic drive. You wouldn't lose any of the drive quality of the standard car.

Remember that you ought to look at brakes and suspension when going that far though.

I don't think I have forgotten anything.