Royal Tunbridge Wells, to give it its full name, is Received Pronunciation Central, archetypally the most conservative town in the whole of England. It may not have been that way when your dad’s ancestor left of course.
I was there for a wedding a couple of summers ago and found it a very pretty town.
Yeah, I had a hard time reading what he wrote, so it is probably Belper.
I seem to recall Bubble’s accent labeled as rural Lankashire(sp?)?
(The Chilterns, actually). 
Yes, the Rossendale Valley is in Lancashire.
Gulp. Blame the beer. Alice’s accent doesn’t sound like anyone I’ve spoken to from that area (my brother used to live in Chesham, btw), but I seem to recall that Pam Ayres is from Oxfordshire, so maybe that’s right?
Both Lock, Stock and Two Smoking Barrels and Snatch are both set in London and many of the cast have genuine local accents (not Brad Pitt’s gypsy of course ;)).
There are a lot of immigrants to the area with Lunnun type accents, as well as middle-class types with RP, that are eroding the proper Oxfordshire accent. Chesham’s Buckinghamshire (IIRC) and closer to London, so the rural accent would probably have been eroded quicker. However, in the village where I grew up, most of the people spoke like Pam Ayres (well, she was exaggerating it). You can tell Oxfordshire from other ooh-arr accents by the peculiar vowels:
Post becomes paste.
Boy becomes bee.
Loud becomes laid.
How becomes ay.
So, who can translate this from Oxfordshire dialect:
Ay laid did the paste bee shate?
“How loud did the post boy (=postman?) shout?” would be my guess. I can just hear it in the “I wish I’d looked after me teeth” stylee.
Chesham (or Trumpton as my dad called it whenever he went to stay) is in Bucks and is indeed full of immigrants from The Smoke due to it being on the Met line.
On the subject of Black Country accents I have been told that , because this area is actually made up of a collection of villages and small towns, that there are many accents. It has been said that a resident of that area can almost say to the nearest street where somebody was born just by hearing them speak. I had an uncle from there and his accent was very pronounced , sometimes I had difficulty understanding him.
Accents do change in a very small area . I was born and raised in Coventry and that accent is different to Birmingham twenty miles to the west and Leicester twenty miles to the north east.
To clear up something for our US friends , when we talk of the Black Country ( west of Birmingham) this has nothing to do with race or colour of the inhabitants but to the fact that this is a very industrialized area . The “black” comes from the industrial pollution of the past which has been mainly eradicated.
Isn’t it Durham?
This site says it was shot all over the North East, and although it mentions Easington, there are towns of that name in Northumberland and Cleveland as well as Durham and it doesn’t say which one. There is an Easington Colliery in Co. Durham though, so you’re surely right.
Jamie Bell is apparently from Billingham near Middlesbrough, so technically his accent isn’t quite a Geordie one, but his gran is played by Jean Heywood who’s from Blyth, so hers is.