Paul Meier riffs on Received Pronunciation or Standard British English, up and down the scales from Cockney to the King, and demonstrates nuances of class, profession, and fictional style. There are some good tips here about using different variations for historical and fantasy characters.
It's a fun listen, well worth the low price, and I think frequent re-listening might instill a bit of the rhythm and character of the dialect in an American speaker. But there are no exercises here, nothing to actually guide an actor or storyteller in developing this dialect. Don't mistake this for language training or coaching. It's not. That, you have to pay a lot more for.