Independent George, on 26 March 2012 - 09:31 AM, said:
I'm not an expert by any means, but what I find interesting is that they sound to my American ears to be not only British accents, but regional British accents. The North sounds vaguely Scottish to me, Robert sounded like he was from Northern England, I know the DVD commentary track to episode 6 said that the Vale was cast as predominantly Welsh (though I couldn't identify a Welsh accent if my life depended on it). I believe (someone please confirm) that Liz Dickie is herself Scottish, but Lysa Arryn seemed to have an English accent to match her sister. Obviously for casting purposes, it's impossible to be completely consistent, but my general impression is that there was a distinct effort to maintain regional accents.
They are indeed regional British accents, at least in part. The majority of the actors portraying Southern characters seem to have a very "standard"/ "neutral" English accent- I'm afraid I don't know what the precise terminology is, if anyone can correct me. Most people I know with this accent tend to be from the South East. The Lannisters and the Tully sisters, and the four youngest Stark kiddies (presumably due to their teachers and mother's influence- or, in a more meta suggestion, it being harder to find kids who could both act AND adopt a Northern accent) all speak in this way, as do Maester Luwin and Septa Mordane- I presume neither of them are from the North initially. Many of the courtiers in King's Landing seem to, too. With some actors (NCW and PD jump to mind) some of their real accent slips through at times, but I believe this is what they're aiming for.
The actors playing Northern characters, by and large, have accents from the North of England (NOT Scotland, just to clear that up- there's a very distinct difference to British people, but in fairness, I'd have trouble separating many Northern US accents myself, so I can kind of understand where that comes from). Which kind of makes sense- if you're going to put British accents in there, at least keep the regional accents consistant

Ned, Robb and Jon all have this accent (though only Sean Bean uses his real accent), as do characters like LC Mormont, Greatjon Umber, and Bronn. Alliser Thorne and Yoren are also Northern, I assume this is because their characters are intended to be so?
The Vale is, apparently, based on Wales (though Lysa Tully is the main "speaking part" in the Vale, and has the "Tully standard" accent, if you like)- Ser Vardys does indeed have a Welsh accent. Littlefinger does NOT have a Welsh accent, despite being born in the Vale, though he did spend most of his childhood at Riverrun, which would likely explain this (assuming this was taken into account).
Pyp has a slight London/ South Eastern accent on the show, from what I remember? I can't narrow it down for you any more than that, but it's from that region. I'm not sure where Pyp is meant to be from in Westeros.
Robert's accent is a mystery, given that it is Northern, not neutral like his younger brother, nor Welsh (since he was raised in the Vale of Arryn, this could make sense). One could suggest that Ned rubbed off on him, perhaps? Sam Tarly is also an interesting case, he seems to have a Northern accent despite being from pretty far South.
I'm wondering if they're going to continue with the regional accents, and have another for the Dornish characters?
For an example of a Scottish accent, listen to Richard Madden or Kate Dickie in interviews, both of them are Scottish but alter their accent for their roles.
Hope this helped!
As for British accents in fantasy... well, in some cases- like Robin Hood or Arthurian legend based tales- it makes sense since these are actually set in Britain, and whilst the accents have very likely changed over time, for the viewers in the modern day, it ties the characters nicely to the setting. A lot of fantasy seems to be set in a mediaeval-esque time period, which is likely associated more with British accents than American, despite the fact that mediaeval Europe contained many countries. I can't really speak for why British accents seem to be the norm in cases like the Borgias, though... that's a bit odd...
There is the occasional fantasy film/ series featuring American accents, though- as well as previous examples, I saw "In the Name of the King" recently, which contains both American and British accents (but, more importantly, also contained Blind Guardian songs in the credits...). But I do agree that British accents seem to have become the standard. Personally, it didn't seem odd to me in AGoT, despite their author being American, because I read the books in similar accents- not so much things like the Welsh Vale accents, but the North always sounded... well, Northern, in my head. But then, I'm British myself, so it's probably very different for those who aren't.