Living in London, you become aware of a wide variety of accents. There's no such thing as a "British accent," the thing is plural, beginning with working class or Cockney, going on to Midlands, Scots, Irish, Australian, New Zealander, West Indian, Nigerian, Indian, and more recently East European.
In the old days, there was something called the "BBC accent," used in all public broadcasts, or the "University accent," based on public schools (in the U.S.A., read "private") topped off by speech patterns prevalent at Oxford or Cambridge. And there were also "county" accents, characteristic of the old landed gentry mainly situated outside London. All of these were related, they constituted the speech that was regarded as belonging as a birthright to the ruling classes--and therefore desirable.
But now the BBC announcers use a variety of accents, including one that developed in the 1980s and usually referred to as "estuary." The latter is Essex-flavored and was adopted by younger upper class speakers as a way of not sounding too posh or upper class. It was felt to be more egalitarian.
My advanced degree is in French, and in the course of getting it I learned not only French but also German, Italian, and Spanish. Because I have "a good ear" I can sound quite close to what native speakers in all these languages speak. And I think people in at least France are glad I don't sound like Jean Seberg in Breathless when I speak French.
A long time ago I set myself to learning English as a foreign language, and now know the differences in vocabulary, spelling, idiom, and pronunciation. (A few examples: a cellphone is a "mobile." The trunk of a car is "the boot." The statement, "It has nothing to do with you," becomes "It's nothing to do with you." American verbs in "-ize" like "realize" become "-ise," "realise." Yet again there are class differences in vocabulary, so that, for example, upper-class "napkin" becomes "serviette" in working-class English; and there are several other words that vary according to social status.) When I began examining accents, I discovered, as I said, that there are several. The BBC was the easiest. Hardest to learn is working class or Cockney, which has an amazing range of vocal effects, fun to reproduce to the extent I can. I haven't spent enough time with county people to manage their accent (again, there are differences according to region), though of course it isn't terribly different from the University accent. I'm getting pretty good at Irish, but Scots I haven't made a lot of progress in, no doubt because I don't yet have any Scots friends.
Linguists regard all languages and all accents as "value-neutral," meaning none is viewed as intrinsically better than others. (As speech, I mean. Literary value can be improved by a decision to expand vocabulary, establish distinctions, and move usage and idioms closer to what's logical and clear.) The "value-neutral" idea makes sense to me, but I realize/realise that it's not the common view. Most people of the upper class regard the working-class accent as unfortunate or cacophonous, and most working-class people regard the upper class accent as pretentious or snobby (which, as noted above, resulted a couple of decades ago in younger upper class members' adoption of the esturary accent, to avoid being despised by the majority.)
Meanwhile, as any British person who has lived in America will tell you, the British accent wins a visitor instant regard over there and often enough, lucrative employment--even when the particular accent in question might be considered in the U.K. as a marker of low economic status. Few Americans can distinguish the differences among British accents. So, how should we interpret the American fascination with the British voice? It must point to a lingering sense of cultural inferiority in the U.S.A., part of the same instinct that led people in 1920s Hollywood to build timber-frame Tudor houses in a landscape and climate entirely different from the one that first produced that building style. And allowed the transplanted Englishwoman Elinor Glyn to become the arbiter of what was done and not done socially in the California film capital.
After the social, technical, and artistic achievements of the 20th century, I see no reason for Americans to feel automatically inferior to Europeans, whatever the situation may have been in earlier centuries. By the same token, there's no reason to regard the British University accent as superior as such. I think it sounds good, but so does working-class speech, just as French or Italian or German sounds good--wonderful sonic creations invented by people who weren't especially trying to invent anything. But here's an interesting fact: When I'm in some shop in Kensington, I notice I get better treatment if I use the University accent. By the same token, if I go the the East Street outdoor market here in Kennington and buy a turnip, I'm well treated if I call the seller "mite" ("mate") and use the working-class voice. Prejudices aren't going away just because they are based on unexamined assumptions. At intellectual gatherings, American voice is best, I think, to avoid the supposition that I'm "putting on airs" if I speak British English. (Which, by the way, points to a conviction, consciously or unconsciously held, that the British accent is superior to the American, a superiority I could be seen as aspiring to, but without the "right" to it. Meanwhile, no French person would feel there was anything out of place if I managed "l'accent de Paris" with close accuracy.) Anyway, once it's established you're not an ignoramus or fundamentalist or Bush-supporter, British writers and thinkers are quite welcoming to Americans, so why not provide the vocal marker for your nationality? Finally, during the forty-odd years I've been coming to London, British speech has moved a lot closer to American than it used to be, probably because of the influence of American film, television, and pop music.
I think too much is made of accents, they're seen (or heard) as much more important than they really are. Here, let me back up a bit. I grew up in the State of Georgia and heard two forms of Southern American English throughout my childhood: the English spoken by whites and that spoken by African Americans. I could still manage either today with perfect ease, though I would certainly avoid speaking Black English for fear that people would assume I was making fun. (Too bad, because Black English has many interesting tonal resources and is fascinating to hear, once you get past the idea that it is substandard.) But around age six or seven, my father, thinking maybe I might one day get a degree in law, engaged a speech tutor for me, a woman from Ohio, I think it was. So she instilled in me something like a Midwestern American accent, and it may well be that the process of acquiring it was the beginning of the development of a special talent at hearing and producing different vocal sounds.
Those lessons came in handy when at the age of twenty-two I came to live in New York and enrolled at Columbia. There were one or two other Southerners in the program, and I noticed they were quickly cut short when they spoke in class--not because what they were saying was stupid, but because their voices gave the impression they were stupid. Now that we've had several Presidents with Southern accents there's less stigma than formerly about the Southern voice, in fact, it seems to be something of a plus. Although: wasn't it in Alabama, during the primaries, that Hilary Clinton spoke with a Southern accent and came in for criticism? Ah, but she wasn't Southern by birth and was therefore dissed as being inauthentic, no matter if living all those years in Arkansas must have made Southern speech patterns perfectly accessible to her. Still, how is varying your speech different from doffing your suit jacket and walking among steel workers with a blue-collar shirt on your back? People like to see themselves reflected in those they meet, to hear from others what they themselves speak. Whose fault is that? If you're running for office, a gift for different accents might be useful.
I still think too much emphasis and concern attach to accents, but no doubt that's like saying people worry too much about clothes. Self-presentation to outsiders is one of the most powerful motivators in experience, and that's not going to change just because a little reflection shows that there's no rational basis for fears that we're unworthy if wearing the "wrong" kind of outfit and speaking in a way different from those around us.