Northern Ireland

The borders will be determined by agreement with England initially.  There remains a hard border between Scotland and the EU.  If Scotland were to join the EU, there will be a hard border between Scotland and England, although it to be hoped there will be an agreement as with Ireland for free movement of people between the countries.

Certainly it will diminish the international standing of England.  There are risks for both countries.  Emotionally, the shock would be profound.  For Northern Ireland, a UK shorn of Scotland would hardly make continued adherence to the union more attractive.  It is suggested that Scotland generates 10% of UK income with 7% of the population.