there's a little place on Leather market Street, where it joins with Bermondsey Street. Nice buch of guys, and very reasonable... they don't do their won MOT's, but will do the work, and take it for an inspection.
We have been using a nice garage called Southern Motors in Rossiter Road, Balham for years. They do MOTs and are really reliable and helpful. It sounds like a long way away, but is close to the Northern line, so works.