I grew up with Marriott Edgar, and would read him at school, in the manner of Stanley Holloway, until I was banned by a Mancunian colleague. She also told us that we were pronouncing bath wrong, according to her elocution teacher, and she couldn't grasp that what said teacher meant was that it was wrong for her, not us, and we weren't inserting an 'r' in it anyway.

Have you ever tried reciting 'Albert and the Lion' in RP? Corpsing is the least of it! Estuary is slightly better.

I'm one of those who picks up accents a bit without trying - and I can feel the shape my mouth needs to be in directly from the sound. Care is required so as not to make people think mickey is being taken. And I can't do it with the singing voice, anyway, so it doesn't arise with songs.