Electrical breakdown

[NickF]

Hi, I have an 2001 A4 Cabriolet 3ltr S

 

The other day when I was driving, the (non factory fitted) alarm started going off intermittently. When I got home i discovered that the windows wouldn't open, the hood wouldn't open and the central locking would not work. The alarm kept going off and I managed to stop it by opening up the boot using the key. I took the car to my local mechanic (non Audi specialist) and he seemed to put it down to the control panel that is in the boot. Damp has got onto the panel possibly through the broken os light housing unit and caused the alarm, central locking, electric windows and hood mechanism to play up. 

 

Has anyone else had this problem if so could they give me an idea of what the problem is and how much it is likely to cost me to rectify?