@SerendipityJane I lived and worked there for a couple of years and have a number of Irish friends and relatives and extended family. I would put money on reunification happening in my lifetime, instigated by Ireland. (If COVID-19 doesn't get me I reckon I'm about halfway through my life, based on family patterns of longevity).
The DUP have been a very convenient diversion for Westminster, and I can hear their ancestors spinning in their graves that they did a deal with the Tories. (And can anyone track down that billion quid they're supposed to have had?! In real, concrete, this is how it's helped ordinary people terms?)
As for breaking treaties, it's not like we don't have a track record of it. If I weren't English, I wouldn't trust the English government as far as I could throw them, after the behaviour on show in recent years. (And historically, come to that.) Actually, come to think of it, I AM English and I don't trust them.
The South of Ireland will continue to be part of Europe; the North of Ireland is already set to suffer dramatically under Brexit. Perhaps the most die-hard unionists would care to come and live in whatever's going to be left of England.