> In France who has the right of way? The car that is already in the roundabout or the car entering the roundabout?

Actually it's pretty consistent all across Europe. Almost everywhere, every entrance to the roundabout has the yield sign [1]. Without the yield sign, every incoming traffic is right hand traffic and those already on the roundabout have to give a way.

Now the trick is that yield signs at the entrance are so common that drivers assume they are always there.

[1] https://en.wikipedia.org/wiki/Yield_sign