I wrote a play, Horseplay, which won a competition but was never produced. I was close once when a member of the writing group I used to be associated with, a rather formidable lady of a certain age, took the play to The Bristol Old Vic and told (probably ordered) the Artistic Director to read it. He phoned me and I went to see him about the play. He was interested but it was, for Bristol audiences he felt, "too Welshy".
So it was - is.
There is an actress in Gavin and Stacey who, according to an interview in a colour magazine, could not get a job for a long time because she was told she was "too Welshy".
You can have a Midlands accent and be acceptable, or a Scottish accent, but not a Welsh one.
This girl is in a comedy and I wonder if, because it's funny, she can succeed because her accent is, to some people who aren't Welsh, also funny.
Yet Richard Burton succeeded, and Anthony Hopkins too. So....... ?
I don't have an answer to this riddle.