400bhp really needs a 200 block IMO and I personally wouldn't feel comfortable taking it anywhere who said differently, as the 205 block tends to crack with the boost pressures needed to achieve a genuine 400bhp.
Once you have a list of people on here that gets recommended, I would phone them up, speak to them personally and get a feel of who will offer you what you want in both service and cost
.
I personally use Harvey at SCS (based in Peterborough) 01733 576 614, but there are some other good people getting mentioned as well. However, be aware that costs can escalate and you need to advise your budget and tell people that you want everything to be included in your budget that will be required to run the car, as some may quote for a bare engine and sound cheap (but when you add the turbo, management, loom, intercooler, clutch and brakes, will be more expensive) and some may quote for everything and appear more expensive from the outset. So always make sure your quotes are like for like by getting a list of what it does and doesn't include.
As has been said, 400bhp really does warrant an RS500 intercooler (the standard 2wd one is spent at stage 1
). Obviously if it was painted black, people wouldn't be any the wiser unless they were Cosworth people, as they would just assume it was the radiator
.
However, to do it properly and to uprate all the other parts accordingly (brakes, suspension, clutch etc), it WILL cost THOUSANDS to do in one go!
Personally, I would be inclined to start with a swap to a 4x4 intercooler and stage 1 chip to see if the quest for 400bhp is for you
. I say this, because 400bhp on standard size wheels / tyres is pretty fucking suicidal
.