off the shelf kits for a 1.6 turbo / zetec-se engine from a mk5 fiesta, costs about £3500. and you wont even see 200bhp...

100% of the time id say get a 2.0 zetec engine and turbo that. Or follow Karlos' guide on here for the turbo conversion using the st170 bottom end st170 valves springs in a blacktop head an a 1.8mm focus rs headgasket.

Much better gains for less, or the same kind of price.