As someone else who currently lives in the UK, this is not true.
I know a bunch of British people who've visited the continent, and the only place they could think of to visit was Normandy, Dunkirk or the Somme. Their entire mental framing of Europe is around the wars, and their grandparents or great-grandparents. And the poppies! Always with the poppies.
Insularity is real and many people, possibly a majority, outside the major metro areas are deeply incurious. The wars are the biggest semantic nodes in their heads associated with Europe, followed swiftly by something about bent bananas from Brussels.
Secondly it is a bit insulting to blithely state that anyone from a non-metropolitan area is some sort of country bumpkin thicko.
It's not even ignorance, per se; it's disinterest, combined with prejudice, in the literal sense of judged before the evidence.
The kids going to Ibiza are just visiting a sunny British resort with funny accents. I'd barely consider that abroad, for the amount of cultural adjustment it entails.
Secondly, I wouldn't even say British holiday making habits are especially different to those of other major European nations. If you want to paint a picture of the UK being uniquely backwards and insular then fine, but it doesn't seem to be based on anything outside snobbery and prejudice.
It is easy to claim that people you disagree with have all kinds of moral faults, but in doing so you become what you affect to criticise.
That part. It was a long time ago.