Are you really saying this could lead to war between Europe and the UK? That seems entirely unlikely unless some other major disaster happens, and in that case they would just quit the EU anyway if it suited them.
Not necessarily between the UK and the EU. But I fear that Brexit is the first step in the dissolution of the EU. And I can certainly imagine a future conflict between, say, Austria and a Russia-oriented Hungary. Go look at the distribution of minority nationalities in Europe, and you will see an endless potential for conflict. That was the reality from 111 AD to 1945.
