I'm planning to purchase a custom build for every day commuting, getting around, and generally enjoying, but need to get a bike fitting first, to get some ideas on frame size, etc., etc.
Can anyone recommend somewhere I can get this done in London?
Hi, I've never used them, but this place concentrates on fitting and custom bikes, London WC2 Holborn/Covent Garden
Not sure if you're looking central London only, but I know that Sigma Sport in Kingston (SW London) do bike fitting services.
Depending upon what level of detail/precision you're after... I'm not sure that they specifically advertise it, but I know they do a "basic bike fitting" service where they measure you & get a print out of what your bike geometry should be (I had that done) but they also do a "bells & whistles" called BG Fit (see http://www.sigmasport.co.uk/BGFitting.asp)
Can't remember pricing but the second is a lot more
Hope that helps.