Renault are terrible with their towing limits as you stated.
A few years ago, I was lucky enough to come into some money from my nan that had died and me and the wife chose to but a brand new caravan and a brand new car to carry us all about. 5 of us. so we chose a 6 berth caravan and then took the brochure to a few dealers to see what car would be OK. We ended up buying a Renault Grand Scenic that would pull our van all OK.
Well after the first trip to France and having the car loaded up with all 5 of us and all our summer holiday stuff, we found the car struggled.
After some research we discovered that the Renault could ONLY pull HALF its towing weight once anyone else sat in the car as Renaults figures are quoted as 'Driver Only'.
After loads of legal stuff, and The Caravan Clubs legal help, we got a letter from Renault, stating that we would be OK it we stayed within the Gross Train Weight.
Our problem was that the weight of the car, weight of the caravan and out stuff meant that to keep within that limit I could tow the van only with me and my smallest child in the car. The wife and my two oldest couldn't get in. So Renault had sold me a car I could use...
After what seemed like months Renault gave me a free upgrade to an Espace which could tow us and my family, but the car was 12 moths old and not new as we had with the Scenic.
I still have that Espace and we have towed all over the UK and France and Spain ad its been OK.
Be very careful of their quoted figures...