Bert said:
I've checked the energy drawn from the grid when plugged into a 240V outlet and once the control box starts flashing, it pulls only 2.5W from the socket. As mentioned by Regulo, this would be the standby rate of the control box, not the car. Leaving it plugged in and turning on the car for a minute will actually restart the charging for a few seconds. The control box still senses the battery fill-grade in the car and re-charges accordingly.
Cheers,
BERT
The charger is in the car - the control box in the cable contains very little and does equally little. It contains relays and electronics to detect connection faults and cut the power to the car. It also contains a signalling system that informs the charger in the car of the maximum current it is permitted to draw. The same functionality is included in the dedicated EV charging points that you can have installed on your wall and in the fast (not rapid) chargers you find in some car parks. I believe that the control box in the cable that ships with the car encodes a maximum current drain of 10A. Fast chargers will encode either 16A or 32A - though the PHEV charger will never draw more than 16A (actually rather less, if I remember correctly).
The control box does not get involved in any decisions of whether or not to charge the battery, or how much charge to put into it.