Calma. Coming out of the EU is not like having global sanctions imposed on you like North Korea. Its not like the UK is isolating itself it has just chosen to be out of the free trade arrangement within the EU. Its businesses can and do still trade with the EU. One of the arguments put forward in favour of Brexit was the ability to set up its own trade agreements with countries like US, Japan, China etc rather than being restricted to the EU ones already in place.
Whether better deals are entered into is a different issue but the ability to take control of its trade an open itself up globally was one of the points pro Brexit campaigners were pushing.
But if you come to me as a business promising me $10M in revenue as opposed to another business (or political entity) representing $100M in revenue, guess who I'm going to work that much harder with to appease a business relationship and strike a better deal? That's basic economics. Hence why the free trade excuse seems fundamentally unmoored from reality to me.
Meanwhile, the idea of insulating borders from the outside world -- perhaps primarily driven more by North African and Syrian immigrants in Calais and the Polish plumber down the street --
is something in common with the isolationism of North Korea. You cannot deny that dog whistling was heavily involved in supporting Brexit from this angle.
And even if you reject any race-baiting angle from rural social conservatives, the demographics of the Brexit vote tell it all: globalist, multicultural Londoners were the enemies of the state, so let's cut off its oxygen supply. Which requires pretending globalization isn't going on beyond your borders. Which is, well, Myanmar and North Korea.