I can pull the fuse that runs the dash module, radio and buzzer (whatever that is?) and my battery can last months, I removed the radio it made nil difference, I think it's the caerbont gubbins.
I have a ctek Bluetooth battery monitor that I used to help trace it.
It maybe worth your while having a look and see if that is a similar issue with yours at least you could play with it at home over winter to see if it's a similar fault if the starter isn't at fault.
