the jackson supercharger kit will take a 1.8 to 200bhp quite comfortably (you really need to fit a decent exhaust system aswell though) and its £1500 from USA. it comes with the bigger injectors and all you need, but the chip it comes with doesnt work on the UK ECU so you still need a chip/remap of some kind.

its not dead cheap but not totall bank emptying either, and you can remove it if/when you sell the car and sell the kit on for decent money.

i've got this system on a mondeo zetec and am pretty chuffed with it TBH.