Haven't seen it, but I'm told that Billie Piper's take on a Belfast/Northern Irish accent is altogether something to behold in its terribleness.
Apparently, her character 'Bronagh' said in the first series that she was 'from the Shankhill'. Seems unlikely; that part of Belfast is very much a Protestant one, and Bronagh is very much a name given to Catholic girls. Oops.