Hi Ian
Not sure what part of London your in but I use the following garage based in SE London. I have used them for cambelt change, service & MOT and have no problems recommending them :-
Albin B Motors Ltd, Unit 2b, Maybrey Works, 2, Worsley Bridge Road, London SE26 5AZ
Contact : Kevin Barnett.
Tel: 020 8650 7080
Email:albinbmotors@btconnect.com