Despite the house being on a hill and away from all the flooding in Leeds, the rain water still managed to get in an kill my CCM unit.
The leak was identified as a cracked and leaking pollen filter housing and this was probably what my steam and AC issue was (see other thread viewtopic.php?f=2&t=113981).
Here is what the worn out pollen housing looks like from below...

And the top...

As you can see the gasket has worn out and there is even a crack in the unit. Water managed to get in and with the heavy rain it reached the CCM unit which for those that don't know controls the central locking, windows, remote keyfob etc. My first sign was that the alarm kept going off over Christmas so went out to have a look and initially thought the fob as dead, but as I realised the above wasn't working decided it was the CCM (Grizz did help me with the diagnosis).
This is quite a common problem in the C5, so I would go and check yours today as well as that plenum valve.
First issue was the doors were all deadlocked, I managed to open the drivers door to get in, but the CCM is located under the carpet on the passenger side. To get to it, I needed to remove the glove box, and some trim on the side. Then, with a dose of luck the carpet came away and then I saw the CCM box and it was quite wet. With some loss of skin on hands and some swearing I got it out, and it had a lot of water in it. No point trying to dry this out...


Dehumidifier and a heater in the car now for the last few days to dry out the carpet and a new pollen filter housing and CCM ordered with my local TPS, but does anyone have an idea how to code the new CCM module? I have a vagcom luckily.
R