Fairly sure this has been asked before & that the answer was Freyr or one of the other crags in that area. But if you are willing to travel a little further there are more crags in Luxembourg (Bersdorf), the Vosges & no doubt others.
Well, that got me looking at the ukc crags map, and if it has to be French (as opposed to obvious candidates like Freyr or Berdorf) then St Vaast Les Mello must be the closest. And looks like some kind of French Pex Hill. Brilliant (maybe)
In the bad old days of foot and mouth, we did a really enjoyable weekend trip to Clecy in Normandy. Lovely camp site (at least it was back then), very picturesque and pretty OK climbing.
