[English; lived in Scotland for 3 or 4 years]
[Edit: Interesting reading the comments. Maybe things have changed (though I would have thought the debate over devolution - which seems like a good idea to me - would have exacerbated feelings). This was ~15 years ago and many Scots explained it to me as resentment over Thatcher, poll tax etc (in fact, one reason we went to Scotland was in search of a more left-wing environment). It wasn't good natured ribbing and it was pretty widely acknowledged as being "a thing" (had many conversations with Scottish friends about it - one memorably said that it was considered normal in middle class conversation over dinner to trash the English in a way no one would dream of doing to any "racial" goup). And I could certainly understand the motivation (the "historical context"), even if it was occasionally unpleasant.
It also got considerably worse when I moved from academia to "real" work.
It wasn't trivial (any once incident, sure, but the steady drip over time...), it certainly wasn't isolated pockets, and it's something I would take into consideration in future. In short: I was glad to leave.]