As Mike C said; there's a good website on doing a budget conversion which is worth a read. It will give you an idea of what's involved in it, and some rough costs, so you can decide what you want to do with it. I personally wouldn't go above 6/7psi without a decomp plate myself, as that's what I've always been advised.

You can do a reasonable budget one with a decomp plate and 200bhp is possible, but it needs to be mapped spot on, as any kind of detonation will soon blow the standard bottom end to bits. So I certainly wouldn't skimp on management and I'd have the set up work done by someone who knows what they're doing, so that will obviously push the cost up a bit.

But for the rest of it, you can just rob parts from other cars really. Focus RS exhaust manifold fits straight to your engine, you can use the Focus turbo, or adapt another T25 from a 200SX or something. Use an intercooler from another car, or one of the ebay jobbies with all the pipework. Injectors are available from other cars and can be made to fit. You don't need to bother changing the standard inlet if you're not going mad, so don't waste money there. There will be some fabrication involved, but if you know someone who can do it for you, it shouldn't cost the earth. Like I said, the big payment will be for management and mapping. You'll also need uprated valve springs unless you're using a tiny amount of boost, so factor that in too.

At the end of the day, ignore everyone above telling you to buy an S2 or something else and do what YOU want to do with it. Work out the cost, and if you think it's worthwhile, go for it. It's your money, no one elses.

Personally, I think if you can do it on a sensible budget, go for it. No one expects a MK6 Escort to be quick, so a turbo one will really surprise people, and even a properly built budget car can give pretty decent performance. I seem to remember the car Mike C mentioned above was timed in the mid-6s to 60mph, which isn't half bad for a car built on a budget. I'd take a 200bhp turbo GTI over most S2s any day of the week