Off on a slight tangent - I find it interesting how some people's accents change over time when they move to another area whilst others either remain unchanged or actually becomes stronger.
Having been born in Northumberland and then moving South at the age of 16 (returning once for a brief period of 2 years since) most of my original accent is pretty much gone. My vowels remain a little flat and people know that I am from 'somewhere else' but its difficult for them to immediately pin point where. Ive had some interesting suggestions over the years ranging from Wales to Norway.
I know two people from the same part of the NE who have lived in the South East for as long as me. One now has no trace of a northern accent and people assume he is from the home counties - the other has retained most of his traditional accent and is easily identified by most people as being from the NE.
I recall working with a chap from Paisley a few years ago whos accent was so strong that most people had to keep asking him to repeat things so that they could fathom what he was saying. One day I was talking to a chap who happened to have gone to school with him - he told me that his original accent was no where near as strong and seemed to have become more Glaswegian since moving to Berkshire.