Last night as I stopped at the petrol station, I accidentally left the headlights on, I thought they were on auto, but they weren't. Never mind I will only be 5 minutes, so I fuel up and go and pay. Upon returning to the car, it hesitated in starting and it appeared that the battery was dead, turn the key nothing. So I took the key out, unlocked the car again (already open) and it started.
Today it did a similar think with the sat nav charger powering up the sat nav.
So I am thinking if there is any drain on the battery, the car won't start. If you remove the additional drain, its fine . . . weird !