Hey listen what just happened with me yesterday 
As previously shared that I serviced my both front doors and discovered central locking motors present there but not working. As seen in this pic.
Yesterday when i was parking my car after getting back from trip, I locked my side door and suddenly, from no where, all my doors got locked
... In surprise I unlocked and locked driver side door couple of times and VOILA ... central locking was working
... I think spray of WD40 worked well on the electrical contacts and other parts inside the door.. feeling happy 
Now please advise me some good alarm system and price... someone told me to get BOSS security system as steel mate consumes more battery that boss... I think Normal alarm system is not quite good as when car is out of sight you have no idea if alarm is yelling. Steel mate 2 way system looks great...
waiting for your suggestions