I've lived in Sheffield for nearly 28 years now, but I'll never sound like a Yorkshireman, though I understand the language and they don't bother to check my passport at the border anymore.  (I should explain that I still have my BBC-type accent with a hint of inherited Scots.)  Years ago, I worked at Stanley Tools as a labourer for a few months; "You're not from round here, are you?" they said.  "No." "Are you from Barnsley, then?"

Malcolm