I used Eco Design Consultants in Milton Keynes, no idea how far they cover though. Nothing but good things to say about the input they provided and job they did.
http://www.ecodesignconsultants.co.uk/I retained local architect (onside with Passive House but not skilled) and quality builder (don't care what you want, so long as it is on the plans that's how we will build it) ... but they did need some input from Passive House consultant to be "aware" of things they had to get right. I didn't want to afford cost of full control from Consultant, so he came onsite at specific points in project. Dunno if that was foolish ...
Consultant objected to some design features Architect designed (with Maths to back it up

) and those features were ditched (from memory complicate dormer in roof which had huge thermal loss ... and a fortune in complicated Hips etc

... and also roof-glass (i.e. Velux-type) which he said would catch far too much sun in summer, and be a source of falling cold-air in winter. We were worried that room would not be bright enough, architect told us not to worry on that point, and turns out he was right

)
Love the Passive House. Neither wife nor I have had a winter cough or cold in the 5-ish years since built. Such health benefits are a known feature of course.