I have had a few similar problems to others in this thread and have today stumbled across something that may be worth checking.

So mine is a M57D Manual 6sp 2004. Increasingly it has been randomly draining the battery, and draining it to the degree that even the central locking wont work. I was pretty sure it was a leaky airspring on the back as I had heard the compressor working a few times when I had parked up (on a slope) and just presumed the pressure was dropping through the night and the compressor was running. I needed an early start today and didnt want to have to piss around first thing with a possible dead battery so pulled fuse 80 to the air suspension.

Went out this morning...dead battery again. Got it started and set off and discovered my indicators (turn signals) didnt appear to be doing anything, well not inside the car anyhow, later we checked and externally they were. Occasionlly the green arrows on the cluster would randomly start to fash but then I would turn and the indicator would continue to flash despite the stalk returning to centre. as the journey went on the turn signals seemed to develop a mind oftheir own. Hazzards behaved in the same way. I headed to the LCM and discovered the carpet in that area was soaking as was the cover of the LCM.

The usual thing of the drain pipe coming detached behind the airbag cover hadn't happened and was still in place. But it's cold and raining here in the UK today and couldnt stand it anymore. But..I am sort of thinking now that this is also the problem with the dead battery too. Will pull it to bits tomorrow and report back.

Edited to update: LCM dripping with rainwater and on examination had a few dry joints on the connector pins. Dried it out and re soldered the dry joints and everything worked fine and no more flat battery. used an airline to clear the drain by applying it at the metal pipe where the rubber pipe meets it. Staying dry at the moment...Will keep an eye on it.