Irish tensions are resurfacing now too. A sticking point is the Irish/Northern Irish border. The government is being propped up by 10 fanatical, conservative unionist MPs (not the Tory kind) and have literally tanked what could have been significant EU progress.
Now the feeling is that the unions hold disproportionate power over the UK government and that doesn't play well with a fragile good Friday agreement.
Same story with Scotland. Now that NI potentially had single market access plus customs union, which those in power in NI didn't want, Scotland wants this too. Independence referendum was won based on "better together" and yet it seems they are now being dragged out of the EU against their will.
What a mess!