+1 for above. He'll probably pass you to Chris at CJS, but from what I hear he doesn't do too many now due to how busy the dyno is.
+1 for CJS as he has a flow bench, he also gets Rich at Louigi Moto to help out when he is too busy as they share an industrial unit.
Don't expect them to do any polishing. Rich says its counter-productive and doesn't do it. He says it doesn't improve gas flow but destabilises and splits the air/fuel mixture and an unpolished surface produces better running. Chris also says Testastretta heads are often pretty good already. Slight machining sometimes to equalise the ports but unless larger valves are being fitted there's often little to be done except setting the cams up properly and tightening the clearances which the factory leave pretty sloppy. That's all they had to do to mine. You won't find anyone who'll give you sounder advice so speak to them first about what you're looking for.
To give you an idea of cost CJS charged £400 a while back to gas flow and fit new valves to a set of 748 heads. I felt it was a good price considering the amount of work involved
