I thought that but I thought I would try to kind of disable the motion sensors by using some good old duct tape and it didn't go off last night so it might be that, but what's the easiest way to check the battery mateJust realised most likely cause is the battery is on its way out given the evidence of it just happening during the night. The alarm thinks battery is being disconnected and sets off using its own built in battery.
We live in a cul de sac so definitely no trucks mate but I'll check the contact pads but it's not gone off with the tape over the sensorsNot sure, could be vibration from passing truck, try wiping the contact pads on the sliding doors. Are the rear quarter windows open a touch? You can lock the car using the key in the drivers door handle, alarm is not set doing this.
Yeah if its working OK I'm going to leave itMultimeter no good to test battery you need a proper load test to determine its condition. If alarm problem solved I would not bother especially if engine starts OK if car unused for a week or so.