On the way from Mont Saint Michel to Pleubian there are other lighthouses and time should permit to have a quick stop there.

Pierre de Herpin (ID: 1670)

A very nice one is Pierre de Herpin. The lighthouse is out in the sea but within reach for telephoto lens.

 

Two others are close to Saint Malo.

Chenal de la Grande Porte Ldg Lts Rear Rochebonne (ID: 1676.1)
Chenal de la Grande Porte Ldg Lts (ID: 1676)