I had this problem not long ago, and had my scu sent off to get it checked out.
Try this guy, he is very helpful
http://www.alarmremotes.co.uk/
but mine came up with no faults, and put it down to the key fob. I found it very strange, as it has been working fine the last couple of months, with the original keyfob?
My symptoms were I couldn't start the car, and the alarm kept going off when I opened the drivers door.
