Wave surfing in the Netherlands, Wijk aan Zee/Velsen Noord beach, also known as Noord pier, (North pier).
As far as the locals know it is the only place in the country with useful waves often enough to consider to have gear handy.
It is not a good surf spot, it is the only one that offers any challenge.
Looking at this webcam site, the locals may not know all the locations.
Those locations I recognize all have man made structures on or as part of the coast, although I do not guaranty that there are no natural surf beaches at all.
The Belgian and Dutch coast is sandy beach, without natural rocky bottoms, making for a lack of surfable waves.
No wild camping allowed in the Netherlands and as the few surf spots are in a crowded areas, it is rather likely you will not get away with it. Camp grounds are around but may all be closed outside the season.
I am not that familiar with the French coast and the results there will depend on what you include in your search area.
As mentioned in the comments on the question, dry suits for surfing do work. (They are also for rent in at the Noord pier surfing shops.)
As I do not surf but have worked with someone who did surf on Noord Pier, I know there is a community of regulars who surely have local traditions.
If you do have the time, search for a facebook group or some such, and see if you can find information online. (I can not do much for you there as I do not do facebook nor know what to ask about.)