Hi maybe I can shred some light on your issues,, I too had the same issues, (all be it a Grand Espace).
Mine was down to a badly corroded yellow wire, ( this is the reverse light circuit.)
Mine was off the front of a large connecter block called R262, which in the Espace is in the engine bay down the side of the battery tray. ( it was broken on a bend behind the headlight, from there it runs around the engine to the reverse switch at the gear box.)
I found mine by finding where I had 12v, and where I never had 12v, the I continuity tests to find the break!
One wire and all issues fixed,
I know yours is a grand scenic, but they not that different!!!