Abandoning the UE is not an occasion to isolate from the world, rather the necessary decision to refuse the intrinsically liberist policy Europe is based on (despite all the “social democracy” proclamations), seeing it ( the liberist ideology) as NOT modifiable being it the very foundation on which this Europe was built on in the first place.
GB refused the current EU model, based on the subordination of democratic institutions and subordinate classes to the whims of Bruxelles’ technocrats and on the expoitation of lower classes by who has the means to do that (i.e. international capital).
The only adequate environment on which to restore socialdemocracy nowadays, things staying as they are now, is the National State, where the demos should be redefined not in contraposition to other nationalities but in contraposition to neoliberist predatory élites.
NOTE: I know, London is a beneficiary of international capital but it can be considered almost as a separate city-state with its own rules and economy that’s why is not considered beneficial to the overall well being of GB.