Sorry but Brexit is very much a fascist movement. It is based on extreme nationalism, racism, and xenophobia. This planet has no room for that type of archaic thinking. In everything I see these are the driving forces motivating those wishing to cut themselves off from the world.
That is very much reactionary and counter to what is needed. The great success of the liberal economy was consistently based on elimination of borders, racism, and tribal exclusions. The result of that reaction is inevitably trade wars followed by violent conflict. The wealth that should be redistributed will then be destroyed except for the oligarchs who will confiscate whatever is left.
The range of institutional problems with the EU must be dealt with and it seems that those are structural in many cases. There is, I think, no future for nationalism or the current form of sovereign nations for a range of reasons but mostly because it is unnecessary. The concept of sovereignty applies only to the individual. The fact that direct democracy combining with AI administration has the potential to eliminate the abuses and bigotry that are inherently human.
The need for planetary level organization that is now critical will work best as an alliance of regional administrative groups made up of sovereign citizens committing to crisis climate management. This must be based on explicit charters supporting universal rights for all sentient beings with no limitation to Homo sapiens or current planetary biological forms. We will be very divergent very soon.