Haha great question Snow!!
British accents are very very diverse and yes you can absolutely tell where people are from by their accent. Which is not bad going to say we are about the size of Florida or something.
So you probably have a view on what a 'British' accent is (I'm thinking Hugh Grant etc) but there is actually no such thing! . I'll try and get some examples for you....
There are Scottish (Ewan McGregor), Welsh (Catherine Zeta Jones) and Irish (Liam Neeson) and massive gradings across each of these!
I'm from Yorkshire so very used to that accent - flat vowels etc. (Anne Hathaway attempted the Yorkshire accent in the film One Day and failed) But even further north you have the Geordie accent (Cheryl Cole).
Across on the west you have lanchashire / Manchester (daphne in Fraiser) and very very distinctive is the Liverpool scousers.......struggling to think of a scouser you might know!
I now live in the west midlands which has a 'brummie' accent - (Ozzy Ozbourne!), the south west (in somerset) has a very 'rural' accent.
then you have the Essex accent, which I know you know from TOWIE! London is often Cockney (ever seen Eastenders?)
I've missed loads out but you get the picture how diverse it is!
I'm not sure who is in the Waking Dead.....tell us who the actors are and if I know them I'll tell you what their accent it! Loads of US shows seems to have Brits playing americans at the moment!
Homeland (Damien Lewis - very home counties, went to Eton don't you know

)
The Americans (Matthew Rhys is Welsh)