"Black Sheep of Europe." The UK is notorious for being "with Europe, but not of it." So they take part in Europe in general, but duck out of things like the single currency (Euro), or anything that is viewed as infringing on Britain's right to rule itself (seriously, you could debate on this for days, and that's without dragging the whole "what about Wales, N. Ireland and Scotland?" issue into it). Since Germany and France are the EU's heavy hitters, they're generally the ones to call the UK out on its selective membership, since the UK IS part of Europe...when it suits. Hence, "black sheep", a member of the flock but still standing apart from it.

TL;DR - France is calling England out on his constant "opting out" of Europe.