Thanks for the write up on the fuel flap lock, very helpful.
Unfortunately cleaning and greasing the worm drive didn't work reliably on my lock so delved further and found the connector pins for the motor were a push fit into the motor. There was a black discolouration on the pins and points where they entered the motor. Cleaned this up (used Deoxit d5 but switch cleaner should work) and it's worked fine since.
Pic shows pins and motor after cleaning before reassembly, (ps take note of how they fit into the casing before disassembling
)
v70 fuel flap lock motor.jpg