I don't think they will have a problem fitting a dump valve to your car (it's a very simple procedure!)

Get a quote for the work beforehand and you shouldn't have any issues

(P.S. I've never used them personally but i've never heard a bad thing about them, they may not be the cheapest but the best rarely is )

They've been doing the Cosworth thing for so many years I really can't see you having any problems!