Damien

There would be any number of problems from just closing the borders. Many global companies require the ability for workers to migrate, even if it's just for short contracts, or to recruit uniquely skilled workers for certain jobs. Just as an example we'll be building some nuclear power plants soon and I imagine we don't have all the requisite talents within the UK or newly expanded foreign companies trying to set up here who need to send some of their staff. These will all need work permits at the very least. Then you have issues with people that have foreign partners and what would happen to our own expats should we decide that no more foreigners are allowed in here. We would end up being an isolated island unwilling to recruit, marry or learn from the majority of people in the world who aren't British.

Closing the borders probably would help but in the same way amputating a leg would get rid of your athlete's foot.