If you disarm the alarm you may invalidate your insurance as the Laguna II is fitted with a Thatcham CatII system recognised by insurers as a fairly decent system - it seem sthere is a fault in your system. When or how does the alarm activate - that may give you better clue as to what is happening
As far as I know the sensors are not infra-red but work on a volumetric basis - this is where there are sudden changes in the volume of the inside of the car - as a matter of interest had the sun just come up when at 5am as a change in temperarure will change the volume or pressure inside the car - sounds like one or more of the sensors has gone faulty and has become over-sensitive.
How do I know if my alarm is working on my Lag II ? I have the priveledge model so would assume it has one fitted. I do have the volumetric sensors in the back.
I've sat in the car and locked it and waited for ages and the alarm doesnt go off if I move. I've even tried leaving a window open, locking the car and waving my arm inside - again nothing - its getting my worried that it doesnt work :
Is there a way of disabling / enabling by pressing some keys / buttons together ?