I am sure some use the blitz turbo timer, although I wouldn't use one myself, as wouldn't trust someone trying to nick it round here.
If the engine is std and sound, then depends how deep your pockets are and how much power you want.
As a basic upgrade it goes to stage 1 first around 260/270, with just a chip change, nothing else, though you would be well advised to get a decent exhaust, the chip would be around £150/200 or so.
Most skip stage 2 and go straight to stage 3, which is new map sensor, dark green injectors, chip, for around 320/330bhp chip same price again.
Above this there are so many combos, but the std T3 is the next limiting factor, so a lot go T34 size, etc etc.
A good stage 1 has a massive torque improvement over std, will totally transform the car.
A good idea to make sure brakes and suspension are up to it as well.
Different people want diffferent things try and get drives/passenger in modded ones.
tabetha