Thank you so much Mark 1 and dk6780 for your prompt responses. How frustrating, my friend, Philippe, who is helping has just gone. I'm going to email him your responses. I can't send a photo as he has put everything back. But my memory is that the first bolt was as per the video. He said the second bolt was facing directly to the front of the car, jammed right up against the grey plastic casing for the seat belts ( ie the bolt at the bottom left of the diagram). But I see from this diagram that is the wrong one. I kick myself I did not take photos of what my system looked like with the plastic covers off.
I'm going to send the diagram to Philippe. Maybe he missed the location of the more difficult to access bolt. (He looked at the video once. I thought he had understood, even if it was in English not French.
I imported the car to France from Spain and the only documentation I had was in Spanish. Just today Nissan said they would send me the links to all the manuals in English. They sent me the User Manaul, a Quick Start 'reference' booklet and a Navigation Manual, , but no Service Manual. Mark, have you a digital copy?
All this is stage one in planning the installation of a removable bed, which will go over the double seat in the second row, and enable me to do some modest touring,