Afghanistan almost doubles in population, many people flee the country due to a lack of resources.

Violent crime in the highly populated areas would probably spike, along with massive food shortages. People who have a bit of money probably find their way back into the UK / go somewhere a bit safer.

Half the population of my country (roughly) disappears. Children too young to vote are left without a family, and banks begin to re-posses thousands of homes.

Many businesses grind to a halt without any workers, and many small towns are almost completely abandoned. People flood to the capital and other major cities, hoping to pick up abandoned jobs, and there would definitely be widespread protests.

Definite looting and violence while people attempt to claim some of the lost assets of those deported, and an already thinly spread healthcare service begins to struggle.

Presumably Brexit still happens, since it's already been voted for, and I have a hunch a lot of MPs didn't actually vote for this shit so they have to see it through, and we're cut off from help by the EU. The economy falls apart, and the pound hits all time low.

As things spiral, people with money begin to leave the country to find stability, while we encounter rising immigration from worse off countries, with people looking to take advantage of the new jobs and housing market.

Scotland and Ireland cut themselves off, and refuse to associate with whatever government organised this fucking shitshow. Independence referendums begin, and border control cuts off english citizens, since a lot of people will be trying to move to Edinburgh / Dublin, with Wales beginning to consider something similar.

I'd also expect millions of people with a claim to any Irish, Scottish, or other citizenship to apply for passports and move away.

As for me personally? I'd imagine my job would be in some danger, but who knows. I'm confident most of family / friends would still be around. London would probably become a fucking nightmare to live in so I'd move further north and try to find a better job, and try to save up money to either get a cheap as shit house, or to move abroad.