Brexit is an English rather than a British enterprise. More specifically, it belongs overwhelmingly to provincial England. With the exception of Birmingham, the nation’s great cities — London, Manchester, Liverpool and Newcastle among them — were on the side of Remain. They were outvoted by Leavers in smaller English cities and towns and in rural areas. Scotland backed Remain by a large margin. Pace the Brexiters of the Democratic Unionist party, Northern Ireland voted for continued EU membership. Wales followed England out.So, the British are English, Scots, Northern Irish, and Welsh. Only two of these four groups, the English and Welsh voted "leave" while the Scots and Northern Irish voted "remain."
Roughly 85% of the U.K.'s population is English, while the Scots are less than 8%. The Welsh are less than 5%, and the Northern Irish around 3% (source: CIA World Fact Book).
The Brexit vote was a straight plebiscite of U.K. voters so winning a majority of the English and Welsh votes meant winning a majority of 89% of those eligible to vote. It was enough to pass Brexit.
The upshot of this is that the Scots may think to leave the U.K. and seek their fortune in the EU. Complicating their choice is the reluctance of EU members like Spain and Belgium - which face internal separatist movements - to encourage secession anywhere in the EU. Presumably the Northern Irish could elect to join the Irish Republic and have no issue with EU acceptance.
Another side note: Looking at who in the U.K. voted in favor of "leave," they are analogous to the people who elected Donald Trump President in the U.S. - the small city and rural yeomanry. Which helps explain his support of Brexit.
