That's why trying to get a religious or ethnic monoculture doesn't work.
If you get rid of Muslims you are left with a multi religious society. If you get rid of all non-christians you are still left with a mulifaith society. In the 1700s Catholics were the big threat within. If you get rid of them you still have all the different sorts of protestants who disagree on everything. And have to decide what the Church of England actually is.
If you got rid of everyone non white you would still have to decide whether Irish people or Jewish descendants were white. And of course the British are very different to Slavic people. And the Scottish would need their own space. But obviously not those basterd from the Macdonalds clan.
People complain about multiculturalism but it's sort of impossible not to have it unless you crack down very firmly on any deviation from the norm a de force people to behave exactly the same. In which case congratulations you now live in a fascist state.