Pleased to see mention above of the Coppers. Bob had a lovely voice and very pleasant Sussex accent.
Not only is there still a Sussex accent to be heard from time to time, but there is also still a rural Surrey accent. Understated rural,not Hampshire, nor Sussex,a bit pinched maybe. Difficult to describe, and not glaringly obvious, but there nonetheless. I hear it sometimes in neighbours. The man next-door tells me his family have been local - well, a mile away in Farncombe - for the last three hundred years. A father and son up the road have a similar accent. They don't sing.
Don't think I've picked it up in 35 years, but who knows.
40-something years ago we might adopt a Scots or American accent or whatever in folk-club chorusing. As schoolboys, we did a cod-rural accent - extreme Borsetshire - for the Bog Down in the Valley-Oh. Wouldn't intentionally do any of that these days.