It won't really affect them. Most of Scotland's business is with England (60%), only 15% is with the EU and the rest is domestic plus rest of the world.

Scotland can't afford to be on the opposite side trade barrier. Opinion polls show Scots understand this - 55% want to remain in the UK no matter what happens.

Northern Ireland is heavily subsidized by England. 26% of their economy is govt spending. They basically can't afford to leave, the Irish Republic can't take on that financial burden and NI can't cope as a small independent state on it's own either.