Welcome to the fold Tim.
Rattles can be a nightmare to sort out, hopefully somebody will come along who has some specifc advice for you.
A lot of cars have plastic or other composite materials now. I believe the rear door on the Espace is some sort of plastic whihc is why the Rear Cycle Carrier they sold for them had to be withdrawn and redesigned 'cos the doors were getting damaged
When do you get you new motor?