What is this talk of "threat"?
Inadvertently you're using the language of Braverman, the language of swamping, the language of Farage, and why? Because you're a racist? No, you're not a racist, you're using that language because it's the the only one available to you, and why is that? Because we've left the field to them, to the racists, so anyone who disagrees with you, and you're not a racist, must be like Braverman and Farage, a racist.
Besides, if there's no such thing as British culture, why does Spain have one? If we're all cosmopolitans in the UK, as Prestwich Blue would have us believe, why would Spain be any different, and if it isn't different, and we're all cosmopolitans, then there's nothing to "threaten"
Oh, and by the way, with you're talk of Scottish-Ecuadorians and Korean-Americans, you've conflated multi-ethnic with multicultural, and why might that be? Because that's what racists do, they believe ethnicity dictates culture, as in "all black are" etc, etc, but ethnicity doesn't dictate culture, as anyone who's spent time with Nigerians, Ghanaians and Jamaicans will tell you. Their cultures are distinctly different, in the same way British culture is distinct from French culture and Italian culture. Except I'm forgetting that the British don't have a culture, so one can only assume neither do the French or the Italians or the Nigerians or the Ghanaians for that matter, or maybe Nigerians and Ghanaians are not cosmopolitans like we are, besides aren't they just tribes huddled together in countries the British empire arbitrarily created? So what the fuck are we talking about?
It's all so difficult isn't it? Talking about a topic where the language is dictated by racists and why might that be? Because we've left the field to them, preferring not to talk about it at all. Besides, don't anti-racists believe talk of culture is nothing more than thinly veiled racism? That must be the reason for all the shit I'm getting in here.
As for colonialism, it's part of our history and therefore part of our culture, well it's part of our culture for those who believe we have one.