[cub]

Apparently accents are pretty 'set' at a young age. If you move to another part of the country, or another country entirely, and make a concious decision to want to change to fit in you will pretty easily.

I moved from the Midlands to the North West but was determined to keep my accent and I have. I've been here years now.

Joss Stone notoriously developed an American twang overnight - as has Nadine from Girls Aloud - so the answer is: yes you can, but have to want to.