Nigel,

The rear doors and fuel flap locks are controlled by the Rear Electronic Module. The fuel flap motor connects to pins B9 and B26 of the REM located in the N/S/R wheel well I think.

Do the rear door locks work ok? Anything else not working like the fuel gauge, fog lamp?

I would check the module for fault codes as I suspect it has an internal fault. With the right diagnostic tool you will be able to activate the fuel flap motor directly. A new unit will have to be programmed in.

HTH

Regards

Sean