(Multiple messages coming in during the typing of the following (and yet another as I typed this). I see some of what I say is relevant to these, whilst a lot is not. Take it as you will.)
And that would be applicable to the situation if we were only talking about 1000 people rather than millions.
Millions, schmillions...
And non-assimilation was much earlier perpetuated by the rules against giving Council Housing to recent immigrants. Quite rightly, one could say, not allowed to jump the queue over natives of long standing(-in-line), but that just highlights the problem of not enough such housing (which Right To Buy v1 didn't help).
So, anyway, with the country only gradually weaned off of "No children, no dogs, no Irish, no blacks, and if you think I'll let anybody cook curries in my houses day-in day-out forcing me to replace all the carpets when they leave...", and immigrants not given randomly scattered council homes so as to 'dissolve' them into British culture, the ones already settled because they had the money to buy homes helped the newcomers settle in homes they get help buying (located near to where the assisting immigrants were, due to familiarity and access and sustaining those original socio-geographic links), and so clumps of immigrants arose, perhaps precipitated to out-movement of original residents to free up more homes, and leading to potential self-ghettoisation in areas, putting extra pressures on links to the 'normal' communities beyond the amorphous borders.
So it happened with the Huguenots, that's how various Chinatowns arose, the themed streets of the Godfather setting, why Corby was dubbed "Little Scotland". What matters is what happens next.
And multiculturalism isn't a bad thing. Multiculturalism
should be that your neighbours might celebrate Christmas
or Hannukah
or Eid
or the birthday of Guru Gobind Singh
or... Heck, they could be Catholic or Methodist or Greek Orthodox or even towards Puritanism (they likely don't celebrate
anything if they're Jehovah's Witnesses, but the ones on my street don't begrudge any of the rest of us, and I suspect they also keep the doorknocking JWs from passing by that often. It might be a 'terretorial thing', but I've known them to have visited my parents' house several times, with nary even a leaflet on my own doormat... but I digress).
What multiculturalism
isn't supposed to be is an assumption that Sharia Law governs a neighbourhood above UK law, any more than I could ever expect to enforce the rule that colanders shall be worn at all times, throughout a Pastafarian community, on pain of meatballs. That is not multiculturalism, that's more of a cultural balkanisation, made all the more unsettling to all other (pre-existing) cultural observers because of the double-whammy of otherness compressed into a handy collection of streets or even entire districts. (All but the "been here since the ice-age" lot forgetting that
their self-identified community was disturbing to the predecessors they displaced or else inherited the Brick Lane-type nexus of congregation and transition from...)
I know there are people with far more vehement opinions about this than I, and I think they're wrong in so many ways. But that's a given, and I suspect I wouldn't be entirely comfortable living alongside them.