Renault Traffic Van 03 plate ALARM ISSUE!!!!?

Hi All, the day my 3yr warranty expired the alarm started playing up. I see there are a few of you out there with the same type of issue. This is what mine does,
If it's parked with the front facing the wind it goes off striaght away, which means every time i park up i have to lock it manually. What can i do (not mechanicly minded!), i've taken it to a non Renault dealer who put it on various tests and they couldn't sort it?? After it started playing up the Renault dealer i got it from put me onto a "specialist" who had it all day and still found no issue!
Any info, ideas welcome,
Thanks in advance :)