This is the handy feature in the fuel flap.
It does mention it the owners book, I found out months later what it was for!!
I think the
part number is BPX 500010 about 2 quid.
Both the filler cap holder and the clip the flap lock solenoid pin goes into are both the same part number.
This is an incorrectly fitted clip, you can see the "tounge" bit isn't quite clipped in.
Try bending the blighter out a bit like this
Correctly fitted clip with toungue tucked in. (can't come off now)