The music hall was a different tradition from the dance bands, Dick. It was the dance band singers like Dorothy Carless, Derek Roy, Len Camber, Georgia Lee, Sam Browne, Evelyn Dall, to name a few who come instantly to mind from all my wireless listening from the 30s-40s that I had in mind. And you will note it was dance bands that I listed in my post. All their singers used US accents. Listen to some old records. They were 'popular' i a different sense from Formy & Lauder whom you mention, in that they sang what was called Popular Music [later abbreviated to Pop], rather than in the native Music Hall genre.

~M~