From first hand experience, every British millionaire I grew up with or know, have left the UK for a country that treats them better.

The only ones that haven’t moved, are those who are considering it, can’t move cause their business is dependant on the UK, or their family/kids need them in the UK.

If your income doesn’t require you to stay in the UK, why would you stay there?

And yet none of the richer people I know have left[0], despite some of them making a lot of noise about it .

Sometimes an anecdote is just an anecdote I guess.

[0] or at least haven't spent any less time in the UK, and are still resident, as some already spend a lot of time in a number of different countries