There are more British people than that living in Spain. In their own little enclaves, refusing to mix with the natives of that country, or in some instances even to bother to learn their language. I would say that the Muslim population is making a better effort at assimilation than large parts of the British diaspora.
And a group of people believing that things could possibly be done a little bit differently is not necessarily a bad thing. Our culture has developed by assimilating different parts (some good, some bad) from dozens, maybe even hundreds of cultures from around the world. We get new viewpoints coming in, that shake things up a bit, then in the good old pragmatic way that we Brits have, we take the best bits of the new culture and add them to our melange.
You are acting as if Britain is some perfect symbol of all that is great in the world, and that it needs to be frozen from this point forward. Personally I think there are quite a lot of aspects of British culture that could stand a bit of alteration. The bull-headed racism that some people can't seem to shift, for one.