I can't help you with your query which centres around France and Belgium, but just wanted to make sure that you know that the answer to night flight is very country specific.
In France I understand (but don't really know the night rules) that night VFR is allowed at least under certain circumstances. In the UK there is no night VFR but you can fly under IFR in VMC.
In Ireland there is no night VFR, only special VFR in a controlled zone, and you need an IR to flight under IFR, even in VMC.
So while it doesn't answer your question, I just wanted to be sure that you understand that any answer in relation to France or Belgium will not necessarily apply in other countries.
dp