Little confused as to what you actually broke but if its the BB shell itself thats died then the only framebuilders of note in London are:
Witcomb Cycles - New Cross/Deptford
Chas Roberts (Croydon)
However Ross down at Brixton Cycles builds frames as a hobby and the guy who runs KiwiCycles (http://www.kiwicycles.com/) works or did work at Witcomb and is based in E9. One of them may be able to help you.
Little confused as to what you actually broke but if its the BB shell itself thats died then the only framebuilders of note in London are:
Witcomb Cycles - New Cross/Deptford
Chas Roberts (Croydon)
However Ross down at Brixton Cycles builds frames as a hobby and the guy who runs KiwiCycles (http://www.kiwicycles.com/) works or did work at Witcomb and is based in E9. One of them may be able to help you.