Goodness, I could have written your post myself OP! My inlaws also live in France (they are French, are yours too?) and are overly excited to meet the baby when it's born. I understand that it's an exciting time, but since we told them I'm pregnant, it's all been about THEM, esp MIL. She keeps blabbering on and on about how much 'she loves babies' and 'can't wait to become a grandmother to have the baby for holidays'. To make things worse, she assumes that I don't know a thing about babies so has cast herself as the 'official advice giver' on every topic ranging from when I will feel the baby move (now, apparently, although nothing yet!) to what kind of pram/toys/bed we should buy.
I know MIL wants to help and wants to play a big role in her first grandchild's life but she too is overbearing and can be quite manipulative. She has 'kindly' offered to arrive a week before the baby is born to do all my washing and cooking for me and has suggested she 'stays as long as we want, a week, two, anything is fine'. Her constant offers of exaggerated 'support', such as staying for two weeks, are seen by everyone else as super kind and generous so that I now feel I can't even refuse them because it would seem churlish of me (as I said manipulative!). I mean, how do I say, 'no, not two weeks, one night will do?'. Everyone in the family would be horrified.
I told my husband I wasn't happy with this, and would prefer that they come when the baby is one or two weeks old, and that they stay in a hotel, but he tells me I am being unfair and denying them their rights a grandparents. Obviously not an easy situation.
Sorry, have totally hijacked your post and don't have any real advice (but the above is all very good so I will be following it too) but wanted to say that I know how you feel. I think the best thing to do is discuss things calmly with your partner - and try to get him to understand how big a birth is and that you don't know how you will feel when the baby is born. This is what I am trying to do anyway. I am also planning to mention my feelings to PILs when I next see them, as my husband is very protective over his mother too, and I know I can't count on him to pass the message on.
Good luck to you