Hi guys, sorry to dig up an old post. i found it while googling. i've just had this exact same issue. i found that the compartment around the battery had water in it. and the drain hole was well blocked.
i also found water on top of some of the loom connecter plugs going to the cabin.
ironically, the large fusebox/relay box, in the batter compartment holds all the fuses to do with the symptoms of the car, and i noticed that the plastic covers are not the most water proof of designs.
i have left the car disassembled for the night, and i will blow it out with compressed air in the morning. fingers crossed that it will fix the problems.
also after reading the replies in this thread, i have decided to hunt out all the otehr drainage points and check them for blockages, just to be safe.