England is occupying part of Ireland. I have no personal opinion about this, or links to Ireland, but it seems pretty obvious to anyone looking at it from the outside.
FYI the term "unionist" refers to those in NI who want the union with Britain to be maintained, not as someone looking in from outside would assume those who want a union with Southern Ireland. Those are "nationalists".
"...have been in Norther Ireland from the 1600s."
Not that it matters to anyone, but the Plantation of Ulster would likely be considered a war crime under article 49 of the 4th Geneva Convention.
Well, probably not, given that none of the states who were, or whose territory was, involved were parties to Geneva Convention (IV) of 1949 at the time.
England is clearly not, since Northern Ireland is a separate country in the UK, not a colony run by the government of England.
After ~400 years its hard to say the UK, is, either, unless you want to say most of the Earth is occupied, often occupied territory of countries that no longer even have a notional government, and often occupied by people who are detached from the government that initiated the occupation (which may itself have ceased to exist.)
The people of Northern Ireland disagree, and we ought to leave it to them.
The Angles are not French nor were the Saxons Germans but both were Germanic, specifically Nordic, coming from what is now Denmark.
There were "French" who ruled Britain called the Normans, from Normandy, which was also settled by Scandinavians and mixed with Franks (Germanics) and Gallo-Roman (post-Romans) (explaining why they spoke French.)
If we do not include NI, then we are just Great Britain.
Most of us are confused about it too.
The Western European Archipelago is a complex place.
By the way, any news on the Scottish independence thing?