Belle used to be rather common and fashionable from the Middle Ages to the 1920's. Now it's less common but still in use. Notre Dame de
Paris probably made it a bit more fashionable :)
Elle is not unheard of, but most people wouldn't use it because it means "she" (teasing at school and play on words to come!), because of the magazine
Elle, and because it's a bit short. French Jews also wouldn't use it because El (sounds exactly like
Elle in French) is one of the names of God.
Ella is more frequent.
Beau is totally unknown in
France. Maybe there were a few
Beau before the 19th century though, when
Belle (and all quality names like
Grace, Bonne, Gentille,
Clemence,
Constant,
Modeste, Parfait,
Innocent...) were extremely fashionable.
I hope it helps!