start collecting bits for a BIIIIG turbo build, do the install yourself and get a proper remap. takes time but £2000-2500 gets you a lot.
Shop overseas, don't be afraid of 2nd hand parts on some items and you could easily build a GT28x or IHI's 300-350bhp motor.
stock internals, need an FMIC, new injectors, new manifold/DP, new exhaust, new turbo and pipework(air and oil/water)