They already do, and have been over-run by Indians and Pakistanis for decades, with an ever-increasing African and refugee population as well. The UK makes it hard for their own people to get benefits, but hands out housing and allowances to immigrants and refugees. You think racism is bad in the US, it's rampant over there. You don't hear about it because the majority of the media is government, i.e. liberal, controlled. Almost anyone with the means moves far away from the major population centers where those types are catered to.
The off-campus student housing I lived in was located in a major Indian/Pakistani part of the city. The entire facility was surrounded by barbed-wire fence and the gates were locked after a certain time at night. That didn't stop our car being broken into one night, and in the time we lived there, at least three stolen cars being brought in and set on fire.
Don't get me wrong, one of my closest friends was pakistani, we planned to join the royal air force together. I had an accident which prevented that, and he ended up flying for the royal navy. Great guy, but he came to visit me at my parents house once, and my dad was visibly hostile.
Edited to add - my parents retired to one of the most remote corners of the UK, which is far away from "those people".. in the years they lived out there, there was a huge surge in Polish immigrants willing to work at a major infrastructure provider. There was much hatred amongst the 'locals' but they didn't want the work.