Judging by the 1965 Triumph T100C (500 cc) I had back in 1982/19 and 83, and the 1969(?) Norton 850 Commando my best friend had ... it helps to be a mechanic to own a vintage British motorcycle ... (or in his case have deep enough pockets for a full restoration. I've not seen or talked to him since 1985. No idea if he still has that bike. I hope so, it was beautiful.) Come to think of it, back in the mid '70's an acquaintance in San Bernardino/Highland, CA. had a Norton 750 TT/Rally Race bike (I forget what year his bike was) he made street legal ... he did all his own mechanical work.
I don't think I ever knew anyone who owned a BSA. (BTW, I was told "BSA" is an acronym for "Bee Itch Stopped AGAIN" by the shop in Davenport, IA, that specialized in British bikes.)