"I'm no Professor 'Iggens, but I have a lifelong interest in, and sensitivity for local dialect pronunciations. I'm particularly fascinated ... essayed the following phrase describing a job offer that paid "noine thewsand dawlers". It made an instant believer of me."
Yes, I've heard the "oi" pronunciation of "i" by characters pretending to be English in US TV shows. It originally took me several episodes to realise that these characters were supposed to be English and that that particular strange accent wasn't just another of the many strange US accents.
"Anyway, years ago I noted that native residents of the Maryland area around Washington, D.C. would pronounce the "u" in ... corruption, until I started hearing British news presenters on BBC doing the same thing with "President Bush" as in "who-o-osh"."
British news presenters on the Beeb exhibit different accents; many of them aren't even English.
"Can anyone comment on the British origins of this pronunciation?"
Something I've never heard. I have, however, heard "Colin" pronounced as "Cohlin".
http://www.dacha.freeuk.com/colour/2g-0.htm
Green Magic
Left Nostril of Ishtar
Genitals in the Clay of Death