i'd recommend Freedom Motorcycle Training.
Their webiste.
I'm in Mill Hill (20 mins from Holland Park) and the school is 20mins from me. i dunno if thats more than you were thinking of travelling but the nice thing is that they have a 95% pass rate as a school and you also get to be away from the idiots that you find in central London areas.
I did a 3day course after having not been on a bike in over 15yrs and passed first time.
Really nice bunch and they took delivery of brand new ER5's on the day i passed so their bikes are allno more than 10months old.
hth
Dunno if i saw your "hello thread" so Hi....and welcome to the site.