Alternative timelines in Western Europe

[mtbc]

I discovered only recently that, before France fell to occupation by Nazi Germany, their cabinet had rejected a substantial Declaration of Union proposed, probably rather too late, by the British cabinet. I wonder what such a union would have looked like and what it would change about modern Britain. Especially, what minimal edits one might have to make to history in order to make such a union actually happen in an effective and long-lasting way.