<font color='#0000FF'>Shame you are in London else I'd have suggested Andy Hayhurst of Dalesdivers (based in Sedburgh, J36 M6) - top chap and doing my B&A 'trox with him in four weeks time.
For sarf' try...
Mark Powell
Dive-Tech: Technical Diver Training
http://www.dive-tech.co.uk
He's on here as "Mark Powell" and if you click
HERE you will link to the YD course he is running. Not met the guy so can't comment but others will after the 22nd Feb no doubt.