Bike fitting in the UK As an keen but casual touring cyclist I'm interested in getting a little more competitive and also keeping myself comfortable over longer distances. So I'm considering getting professionally fitted, as from others' experiences it sounds good. What should I look for in a fitter and where in the UK (preferably the South) can I find a good one? I'm wary of going somewhere that will be mostly focused on selling me new parts or a new bike.

Also, would the measurements be in any way transferable to another bike? I ride a Marin San Alselmo and a Thorn Tandem, plus I'm considering something properly race-roadie as my N+1.

EDIT: I know there are a few sub-questions here and many people won't be able to answer them all, but I'd also be appreciative of partial answers.
You should check out Mountain Trax. They have specifically gone down the route of bike fit and spent some time training in the US with the developer of the system. They are one of the best bikes shops in the south and I would class their service before and after sales as the best I have encountered. 
They are based in Barkham, Wokingham and can easily be reach from the M3 or M4.