I have a halfords high mount that I used to use on a alfa 156.
The straps for the bottom were long and ended in a hook, and I would take them past the bumper and hook them onto something more secure under the car.
The high mount has the advantage of raising the bike above the plate and lights which you are not supposed to block, and that is probably more vital for france.
Another advantage is that the high section can be angled back, mine was parallel to the rear window of the alfa, so the bars the bike rest on are now more like hooks, so unless the whole rack comes off the bike is going to stay on the car.
You should retighten the straps after a few miles from first installation, and maybe check them at periods, but mine felt quite secure and I was happy with 4.5k worth of turner hanging off of it.
I also used one of those bars that keeps the steering straight on when you mount the bike in a workstand (a park one b ut cheaper ones are available).
Nothing was touching the car.