As a Brit, I’m anti-irredentist (redentist?) when it comes to Northern Ireland. I think the United Kingdom would be better off without it.
I have no particular feelings concerning Irish nationalism -- for example, it makes no difference to me whether NI unites with the Republic of Ireland or becomes an independent state, though the latter seems unlikely. I’m advocating purely patriotically, purely for the best interests of my own country. I have no concern for Irish matters.
Scotland, by contrast, I would be sad to see leave, though I recognise their right to do so. And this is not even unlikely, given recent events. But perhaps the Scots can be persuaded to take NI with them? Northern Irish cultural links with Scotland are much stronger than they are with England. That way NI can continue to be “British” if it really insists, by continuing to be part of a country that is part of the island of Great Britain, while the remaining UK can be free of the mess.
Alternatively, if there is no majority in NI for leaving, perhaps there’s one in the rest of the UK? This actually wouldn’t surprise me. We could hold a referendum to exercise our right of self-determination to declare independence from Northern Ireland.