My Ford Focus C-Max (2004) has developed a fault where the battery drains and needs to be jump started. It happened during the colder months last year and has started doing the same over the last week.

I took it to my local Ford specialist, but they couldn’t find a fault. However, Green flag told me that it may be something to do with damp getting into the car.

I was told that the seals have worn and need replacing and that it may have been because of water movement inside the car setting off the alarm sensors which subsequently drained the battery (although I haven't heard the alarm sound).
The fuses have been checked and everything else has been ruled out. Could you throw any light on this for me?