Sorry to veer away from maps for a moment ...

This evening's BBC2 Coast programme was about Brittany and I found the bit about Carnac on iplayer 48 minutes into the programme Coast - Brittany

Although he programme moves fast, they make to connection with Carnac and all the other ancient stone sites around the coast of Britain including Orkney.

There is a brief and exciting snippet of Mark Horton talking to Guillame Robin inside the passage tomb at Gavrinis and comparing the chevrons found on Angelsey with the rock art inside Gavrinis.

Edit: Just spotted some excellent fieldnotes here:
http://www.themodernantiquarian.com/site/10034/gavrinis.html