UK car - 214bhp standard
Import - circa 280bhp standard, and obviously the diffs etc on an Sti will be better. Better suspension etc.

But you could easily buy a standard UK car and have it running 280bhp. Then it'll be slightly quicker than a standard Sti if it's been mapped by someone decent: it's not all about peak figures! All you need then is some good brakes and maybe eibach springs and you've got a great car.