After speaking with my Mum, she doesn't remember exactly the name of where we stayed other than a being a little South of Lyon, but a bit of google mapping leads me to think Logis Hotel Saint Jacques is a likely candidate for the 1979 hotel.
See -
https://www.booking.com/hotel/fr/st-jacques.en-gb.html?activeTab=photosGallery
I think my memory of where the cars were is the private parking bit with the trees now in those shots - streetview gives a good view of the front of the building with outward folding shutters and inward folding glass windows - you can even go inside now (its been done up a bit recently it would seem) - but is still very cheap.
Also going back in time in streetview it looks likely that the restuarant next door was once part of the hotel with pavement seating perhaps ?