as someone that grew up in norn iron, and I am back a few times every year, and with the intention of moving back there within the next 5 - 10 years,
I understand how the border works, it was a hard border when I was growing up, and for part of my adult life there.
we buy more from the EU countries than they buy from us, do you think France, Spain, Germany et al will cut off their nose to spite their face by not wanting to trade with the UK.?
how does the rest of the world trade with Spain etc without being part of the EU.?
they negotiate trade terms with the EU, rather than the individual country, the UK could do that too.
by the way, my own personal view on the violence in norn iron is one that has for a long time now been nothing to do with anyone fighting for a "cause" , but rather one of turf wars, thuggery, drugs, and general criminal activities , hidden behind the veil of ' freedom fighters' , 'defenders of the faith' etc etc etc,