Farrell,
He just ploughed on and on eventually into full IMC for about twenty minutes.
Let me assure you that the above is definitely
NOT 'the way it is' here in France. IMC is IMC, wherever you are, and not allowed for a basic PPL in France.
However, we are talking about
VMC on top, which is indeed allowed in France if you hold a
French PPL. This means you dont have to be able to see the surface, but you definitely have to remain VMC, ie clear of cloud by the distances required by the airspace you are in or altitude you are at.
In your example of a flight from Montpellier to Lyon, if you were clear of cloud as required to stay VMC, you were legal. You however, said you were IMC for 20 mins, which isnt legal.
Regards, SD..