Not much point recommending somewhere in Barnet if you live in Dulwich.
I guess on a 2003 car you are looking more at railway arch garages than shiny glass & chrome showrooms. It's not going to matter about manufacturers brand anymore, just stick with local so it's easier to return if needed. You are in the pragmatic years of ownership now.
What's the work, we may be able to advise?
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TG