Essentially, I'm referring to how some British English speakers pronounce words like "time", "right". That first vowel changes and ends up sounding like "toyme" or "royght". Americans seem to have picked up on it, often laughing at us pronouncing "license" as "loicense", so it's definitely a real phenomenon.
It's something I've noticed among a lot of people, but it seems to be found somewhat randomly geographically - everywhere from the Black Country to Essex, and also in people from parts of the North. Is it a feature of some regional accents, or is it a class/age thing?