I have used http://www.northamptonmotorsport.com
for a rolling road session and they were great. Not the cheapest, but then they are a proper motorsports outfit who set up cars for competitors in a variety of top level national championships.
They quickly worked out that my distributor wasn't working, and whilst I expect some places would have sent me away and told me to get a new one, they went to the trouble of rebuilding it there and then, so that we could get it sorted out and see what the engine was capable of.
Needless to say, I've booked it back in with them to finish off the motorsport prep work (I'd do it myself but realistically with no garage at home, and two small children, it's never going to get done by me), as well as fix the exhaust leak, sort out the fuel mixture and set up the suspension properly.