Top of the list of must-have accents in any drunken carouser's arsenal is the British accent. The British accent is the standard replacement for other accents in movies where characters are from countries that do not speak English. One's level of class and expected snootiness is kicked up ten notches simply by having a British accent.
I never realized that there was so much variation within the subject, though. Honestly, how many different American accents are there? Most of them are from the East Coast or the South so it's very easy to forget about them, at any rate.
Despite the United Kingdom's comparatively small area, it would seem as though every last little town has their own accent. This particular accent serves to identify a British citizen's origins and perhaps class status.
Note: I have no real discernment skills of my own to speak of between regional accents. Of course, I can pick out Scottish hints, but really, I am simply assured that these regional differences are there, so I must assume that such is true.
I have come to a bit of an indignant conclusion that highlighting differences between people leads to new categories of elitism. (Purposeful or not.) At any rate, My Fair Lady makes a lot more sense after learning a bit about accents.