Probably at the start of winter the DIS was showing the boot as open. The connections on the boot sensor were a bit corroded so I replaced the connector and boot lock sensor. There was no sign of water in the general area or leaking from the wiper. Thought that had fixed it then a few months later it started doing it again. In the end I just disconnected the boot sensor and that stopped the problem.
This week we had snow and the DIS is again sometimes showing the boot as open (the sensor is not connected). So now have the alarm going off again randomly. I had removed the fuse for the alarm, left the car for 2 days and this morning the battery was dead. Turns out indicators still flash (presumably when they sense the boot open) when alarm fuse removed. Jump started this morning, dry day, no DIS boot warning till about 70 minutes of driving then after about 90 minutes dash and centre console lights died completely (I have seen this happen once before 6 months ago when I first had problems). Restarted the car, drove home, dash and centre console all fine, occasional boot DIS warning.
Also I only seem to have problems when there is some serious rain or snow.
I was thinking it was perhaps the alarm control unit, anyone know where it lives? Any ideas what control unit does the dash etc? Any other likely control units to look for? Really looking for areas to check for water. I will check under bonnet fuse box again but it was dry previously so doubt that's the issue.
Any advice appreciated. Currently I'm disconnecting the battery if I leave the car for any period of time to stop this happening.