Hi Colin,
Thanks for your response. No, I did check this early on. I think what they are doing is starting the car and moving it out of the garage, turning it off, going indoors, coming out again and driving about a mile to the supermarket, driving it home and turning it off again, unloading shopping, then putting car back in garage and at the same time as all this they probably have the HRW and the heater fan blowing full blast. I think you get the picture . I just think that 14v from the alternator is not enough for this kind of use. I have now turned off the day running lights and tried to give the normal lecture which includes telling him to reverse IN to the garage so that I can get to it if it does go flat again. If it does I have told them I will probably need to replace the alternator. Time will tell.
Regards, Bryan.