finn maccool or disunited kingdom

I appreciated the controversy that the outcome of the Brexit referendum had regionally for the United Kingdom, with a significant majority of Scotland and Northern Ireland voting to remain. I understood how the Scots might try again to declare independence and that Northern Ireland has the only land border with a European Union member, but did not realise just how thorny it was.
Not only is it an unpalatable prospect to have frontiers returned between the exclave of the UK and the Irish Republic and create obstacles to movement and trade, the Republic has extended the right of citizenship to any resident of the island in hopes of reconciliation and ultimate union after so many years of violence and animosity. So called Peace Lines partition sections of Belfast and Londonderry, cities still divided by sectarianism long after the wall came down in Berlin. What would it mean to the notion of dominion if seven out of every ten adults chose to see past historical difference and protest against very recent developments that don’t play their self-interests and trade their allegiances? I am not sure how Britain would react to a de facto reunification.