Paul,
I've recently replaced my OE plain beige mats for a set of black ribbed ones. Beige ones have been in the car since 2004 and there's really nothing wrong with them, just got fed up shampooing them. Plus I got a good deal from MB Brentford in London (incorrectly ordered left hooker ones and they wanted to get rid of them) for £50 and are excellent quality - thick, hardwearing and perfect fit. I find on both types, plain or ribbed ones, that there's hardly any movement (certainly none on passenger side and rears) so really no need for fasteners or clips to hold in place.
What I'm saying is that the quality of MB OE mats , I think you'll find, will vary from country/region to another as they are dealer supplied and not from the factory when the car rolls out. I know UK MB cars have their mats made here which makes sense since we're the only right hand drive country in Europe. In the case of our cars (being left hand only) , OE mats are sourced in mainland EU, so you should be able to get the same ones in France from any MB dealer.
Bing