Literally Brexit was mostly about Brits not liking other Europeans being free to move to Britain, especially Poles.
I lived in London and unless they actually start talking and you hear their accent (or, even "worse" for the average Brit, their language) you can't actually tell a Pole from a Brit.
So. yeah, a fucking mid-sized country in the modern era has left a massive European trade union which gave them massive benefits (it has been estimated that Britain's GDP is growing 2% less every year because of leaving) because of their xenophobia against other Europeans, especially Eastern and Southern Europeans.