How people from one same island make fun of each other's accent

You know too much vodka and Red Bull has been served when Claire's talk-to-random-strangers-on-the-street bug comes out and strikes again.

4:30am
Claire: Where are you from?
Brit stranger devouring gyros: Sheffield. You?
Claire: Manchester.
Brit stranger devouring gyros: What do you do here?
Claire: I teach English.
Brit stranger devouring gyros: AND you talk like THAT!