318 8v convertable cant get the roof down and battery dies easly

I have a 318 8v convertable which runs fine except whenever the door is left open and the courtesy light left on for literally 10mins the battery will drop below 12v enuough for the engine not to be able to turn over. (this is of course with the car not running) Also, the motors for the roof are not working and i cannot get it down. Im wondering could the faults be connected as it sounds like a possible dead short somewhere, probably in the boot? and all the roof button does is flash a red light. Any help would be greatly appreciated. Thanks