to be honest mate i would have thought any garage could do it, i know ford did a couple of different version of the 1.8 zetec, 105 bhp, 115 bhp and 130bhp. but they will all fit, i know the escort gti is 115bhp, and i think the escort si is 115bhp aswell, so it is just a case of one out, one in. depending on how bad the head is warped, it would probs end up cheaper to put your engine in the gti, plus as you say, you have had the cambelt and stuff done on your engine.