Just popped out to try a couple more home burnt CD-Rs in the changer and went to start the car.... battery is flat enough that it won't start. Turns over a few times, but then slows down. Earlier I was out messing with the sound system and changer, only for about 30 mins and never bothered to run the engine... No lights were on, no seat, mirror or window warmers, doors were closed and overhead lights off. Only headunit and dhas cluster were on. To me that sounds like a battery on it's last legs... Last few trips have certainly been more than long enough to replenish battery. Average journey time in the last week has been 25m each time and 20-30 mins. Car has never hesitated to start before now. Add a new battery to the growing list of things to do before the MOT in Dec.