There are plenty of TLs, both good and crap, where Germany wins WW1 and France and Britain are the ones to turn fascist with demagouge leaders.
However I don't buy a fascist France, even on cahoots with a fascist Britain, attacking a victorious Germany. Such a Germany would be vastly more powerful than France, even after a bout of complacency. But what about the rest of France's nieghbours? Would the French Hitler invade Spain, Italy, Belgium, Switzerland or perhaps Thailand, Ethiopia or Persia? I think the Balkans would be part of the German MittelEuropa, and so off limits.