As I put in my post of Aug 11
"The charger lever at the car end has a hole in it so you can fit a small padlock. This would put off the opportunist thief but not one who wanted your charger come what may as the small padlock could quite easily be cut through."
Admittedly the padlock hasp needs to be quite a small diameter but not had an issue even in an urban environment where my mother lives.
As regards padlocking it through the spring. The spring can be dislodged if the flap is bent back on itself (another known issue with the PHEV) and then the padlock could be removed together with the charger. If anything I would padlock through the charger flap locking hole and run the cable through the hasp. This would also prevent the flap from being bent back on itself and dislodging the spring.
Personally when parking on my drive, out in the sticks, I do not secure the charge cable but I do fasten the charge flap to the cable using reusable zip ties. That way the flap cannot accidentally be caught and bent back on itself.