I think "nations" is a good term for them: it's not the same as "countries", but it means more than "regions". England is part of UK/GB when it chooses to be (rugby league, Olympics), or not, as it pleases (rugby union, football).
To describe it as a nation is a useful distinction; and whether anyone approves of it or not, it happens.
I was astounded to see France 24 yesterday say ew monthsthere were 4 “island nations” in the EU: Cyprus, Malta and ... Ireland and the UK. Has the last few months of backstop furore been simply cast aside??!!
"Has the last few months of backstop furore been simply cast aside??!!"
Not at all. Last week it was reported that Jean-Claude Drunker mentioned that "Great Britain" had chosen to leave the EU. They already have in mind a united Ireland and if Mrs May's deal is accepted that may well be what we get.