Hi Folks - Eureka!!!!!!!
Renault Scenic Petrol Flap problem solved by my Friendly and helpful neighbour 'Dennis'. Told me to jack up car and remove arch covering, to which I laughed and told him he was a little crazy. So Dennis jacked up car, removed wheel and undid rear of the arch covering - and yes, we had access to the nuts of the petrol flap (7 mm socket), removed and replaced flap. - not a lot of room to manipulate nuts from inside bodywork . Hope this may be of use to otyhers in the future.
Glad you got it sorted Andy and thanks for keeping us updated