I used to have a posh British voice, and got rid of it at school.
I found it a lot harder to talk and and sing as fast as anyone on the radio, until I changed my accent to an Essex one. It's because when you talk properly, you have to pronounce every syllable and it takes more effort. I can bring it back if I want to, but I generally don't because of the way people talk around here (a mixture of cockney, London and Essex).
Also, if you pronounce the word, "can't" as "carnt" in a song, it doesn't sound as good as "caant". For example, George Michael pronounces it the American way. If he said it the British way it just wouldn't sound as good.
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I've left WP.