Fuel flap.
When I picked up my Stag (had no fuel), I looked for the fuel flap release button.
Couldn't find it, nor could my mate.
Tried to open it my pushing the left side of it, but to no avail.
Had myself, my mate and a dude looking for a way to open the fuel flap at the servo.
Finally gave up, called Ben @ Northshore who proceeded to tell me (in between laughs) that all I had to do was push it on the side.
I sheepishly went back to the car and pushed the RIGHT side of the fuel cap which opened effortlessly
Nothing like having a heap of people looking at your unique (at the time) car while you struggle to open the fuel flap!