What is that called when Helen Love or Rik from The Young Ones pronounces R as W in front of an AH or OH?

"see that girl lying under the bar/ she used to be a wrawk n' roll star"

Is that specific to a certain city in UK? What is it called exactly?

I think it's called a speech impediment.

Woss Disowder

Well, Rik Mayall grew up in Worcestershire, whereas the voice of Elmer Fudd grew up in Brooklyn . . .

It's a standard indie-schmindey student trope. For reference, see also Dan Treacy, Stephen Pastel, Nikki Sudden, Student Grant's posse. Possibly Edwyn Collins too.

"Be vewwy wewwy quiet" is distinct from the R-to-W transformation in "See her running awround/ she's the girl about town that you heard of"

Rhotacism. I don't think it's region-specific in the UK.

"wabbit" very nearly fulfills the conditions in the thread title, but in all honesty I was, like, joking

I know little about English speech-modes but I always assumed this sort of thing was maybe intentionally childlike? Maybe that's just because of Dan Treacy, though -- kind of a mock-vulnerable mock-schoolboy habit ...

haha maybe a posh English Fudd would say it more like "wobbit"

Yeah, but people who do it all the time aren't doing it to be childlike. They just can't say their Rs.

well sure

I do kind of enjoy the image of Dan Treacy trying speech therapy somewhere between "All My Dreams Are Dead" and "The Picture of Dowian Gway"

in the case of Helen Love, it's called "being Welsh"

(or probably some specific regional thing, but I've known other Welsh people to have a similiar very slight version of this)