France was a founding member of ECSC proposed by Robert Schuman, french prime minister, created by the Paris treaty and regarded as the premise of nowadays European union and expanded to up to 28 countries. France played an instrumental/leading role in building the very idea of a community of nations in europe. The contributions of that country toward European institutions are literally countless, but let’s name a few major ones: a shared currency (€), schengen area and absolute freedom of movement for citizens, goods, services and capital (none of which UK took part of). No one can sensibly deny France contributions to pretty much any regulation, judicial/defense/scholar/research/scientific cooperations.

I’m not saying UK played absolutely no role in building these institutions, but they’ve always displayed some reluctancy for further integration. Just fyi, France and Germany have been compensating since the 70s the budget contribution UK refused to make.