Its down to budget I think, if your going for injection. I'm pretty sure the cheapest aftermarket ecu is megasquirt. My mates runing omex on his mk2 zetec.
I'm a skint so i've went the carb route.

IF you can find some one breaking an st170, that way you'll have the injectors-then sticks some bodies on the end.

http://www.mez.co.uk/ms10.html