RE: Ultrasonic Alarm Sensors
I had exactly the same problem on my 07 UK Citroen C-Crosser (which is a clone of the 07 Outlander). These have the Cobra Globe 4800/4900 CAN alarm fitted by Cobra on entry to the UK. Mine seemed to go off when the temperature dropped in the middle of the night! As a temporary measure, you can disable the ultrasonics by pressing the button which is part of the alarm LED assembly on the centre console within five seconds of switching off the ignition, until the LED does a long flash. This must be done EVERY time you switch the ignition off!
After much debate between the Citroen Dealer, Citroen UK and Cobra, they finally called in Cobra to replace the alarm unit and sensors under warranty. No problem since then ;o)