There are lots of good spots all the way from Fecamp to Le Havre (and also all the way along the coast further west but these are close), which is only 100 miles from Paris.
To find the exact ones, and whether waves or flat, I would ask on the flysurfer forum, as you can just write in English and there will be many who can and will answer I think
But of course, if some local can give you a few of the "obvious" ones in that area, in different wind directions, here, it would be great
I assume you ride TT, as it is normally only those riding waves that write about/ask about waves - most TT riders forget this when asking for spots...
Peter