Antidotally I run in to tons of Brits who’ve moved to New Zealand, and they all point to Brexit. Sure lots of kiwis have always done their time going the other direction, but it feels like a trend. Even more go to Australia.
Discussion
This has always been there even before Brexit and it won’t change unless living standard and salaries match those offered abroad. My peers and myself find ourselves all working abroad - New Zealand, Cyprus, Dubai, Kuwait, Australia, the US etc. Why?
Data contradicts this. British emigration is down, and immigration has exploded. 
Yes, the UK has significant problems and those that are down to Brexit are relatively minor.
Brexit was a peaceful civil war and as such, of course people are going to be sore about it for a very long time, with the expected motivated reasoning being applied to every negative fact and figure.