@ABWorsham:
I would love to visit those bunkers on the Atlantic Coast.
One interesting place to see if ever you’re over there is the U-boat pen complex in St-Nazaire, which I visited on the same trip:
http://en.wikipedia.org/wiki/Saint-Nazaire_submarine_base
It’s open to the public, and in addition to having access to the inside you can also go up on the roof to see the Fangrost anti-bomb structures which were designed to detonate bombs prematurely (and channel the blast sideways) before they reached the main concrete slab of the roof (which was itself several meters thick). At the time I visited, you could also visit a decommissioned French submarine inside the pen.