Bottom Line: All the smart people have told us what a catastrophe this will be, and none have said how.
Guess what: it won’t be. A catastrophe, that is.
There are many, many, many countries not in the EU. Now there’s one more.
Any “catastrophe” that comes about will be fabricated out of thin air, because there is absolutely no reason whatsoever that this needs to result in anything even mildly difficult. (You read it first here!)