Ashington and Bedlington were/are the centre of Pitmatic.

North of there starts to become much more Northumbrian, with the soft rolling "r" sound you don't hear on Tyneside (it supposedly comes from one of the Percys' speech impediment) It's a bit like the French r e.g. in "Robert"

The West End of Newcastle, amazingly as it's only a few streets, also has a recognisable accent - I once surprised a hostess at the Dover ferry terminal by telling her exactly where she came from (and she told me exactly where to go...)

Like Suibhne, I can hear big differences in accents in Lancashire in places just a few miles apart - Blackburn and Burnley for example.
Also the names for the humble bread roll change every few miles! - tea cake, bread bun, bap, batch etc