I can only think of Owen Garages in West Sussex:
Owen Garages
Market Place,
Haywards Heath,
RH16 1DB
01444 452890
Never went there myself though, even when I lived in Sussex - always taken my car to Tremona Garage in Southampton or to Steavie in London.
Owen Garages does come highly recommended, though - they've looked after a few FRPs.
There's another one on the list, ABC Motor Sports but I don't even know if they're still in business.