Not local to you, but I've used RaceShack a few times recently and they are very good in my opinion.
Take good care of your car, explain exactly what is being done and why, so you get a little lesson included at the same time.
They also do weekends which often fits in better with end-users. I've just had the TVR Griffith I prepare done there as I was sure it was running too rich and thirsty as hell. I didn't pre-empt their diagnosis by telling them my concerns but on the initial pull, they immediately said - too rich - AFR was between 9.8 and 12.6 and averaged only 10.9 across the run. A change to smaller secondary jets and all was sorted and we picked up another 17HP at the wheels along the way.:thumbsup:
This enabled us to complete a 40 minute race at Brands Hatch on Saturday, with driver change mid way including 2 formation laps (bloody Sunbeams!) and all without running out of fuel - sorted! (2nd in class - 6th overall)
The dyno is at Tewkesbury, ask for Matt as he is the 'Guru' you seek and VERY knowledgeable - also tunes half a dozen or so of the Goodwood Revival cars. He is part time there (as he does other work too) but generally accommodating with appointment requirements.
RaceShack can be found thus -
raceshack.co.uk
Hope it helps....
Oh - forgot to add, cost was reasonable too, at £125 inc - including replacement jets and 4 or 5 power pulls. Obviously more difficult/complicated issues may take longer but always fair pricing IMHO.