Earlier quoted context omitted.
Cursory looked up some ethnographic statistics the other day, and if wikipedia is to be trusted, UK as a whole certainly does not appear to be very ethnically diverse - although London is.
Good for you. Can wikipedia tell you what other countries fair better?
At least 100 countries are more diverse, ethnically, linguistically, racially, you name it. Germany is among them, so is the US. France is about the same level of diversity. A majority of EU countries are more of a melting pot than the UK, in fact.
The UK is 87% white, 95% English speaking, 92% Christian/atheist/agnostic. It doesn't get much less diverse than that.
And of course the places that aren't homogenous (inner London for instance), all voted "remain" by a huge margin.