I left in the 70's
I had a good job, with a company car but I was earning about 2,500 quid a year because of the Great British Wage Freeze ... and my company was hiring people below me at twice my salary. Sure, there's lots of stuff I missed but since my salary in the US at that time was $20k I managed to get by without any problems. I come back for vacations - the currency exchange rate makes it as cheap to visit the UK as many other third world countries.
I've been watching the Brexit debate with casual interest - I have very little skin in the game these days but I can't see the UK making a success of an economy by building a wall around itself. It's never happened anywhere yet and I don't see it happening in the future.
I do find it interesting that the same media conglomerates that pushed hard for Brexit and the same people behind Trump. Good Luck with it.