Originally Posted by LugNut
Had the same thing happen. Like others, probably the main battery is bad (not the remote's). Look for the threads on the battery sizes, and about carrying a 10mm wrench with you so that you too can disconnect the battery to stop the alarm.
As the engine turned over and the interior fan ran at No.3 Setting I suspect the main battery is not at fault.
I keep a basic tool kit in the boot to be on the safe side but as it was cold and dark I didn't pop the bonnet and have a fiddle.
I'm more concerned if this is ECU or Immobiliser related as this will cost heavily to get rectified.