Haven't had many issues although enough to question whether there is a fault or it's normal. Firstly noticed when my car was parked outside on the road and the alarm went off after a loud motorbike sped past (don't believe it was due to sound but vibration? Which may have caused the car to shake I guess or whatnot to set it off). Today went to get my car cleaned and as they were hitting it with the pressure washer alarm went off several times. Is this normal? Can the sensitivity be adjusted or even disabled?
I don't know about the UK but here in the states; the tremor switches for the OEM alarm system is optional - door switches ONLY. One or more of your door switches may need alignment and/or contacts cleaned. You didn't mention if this is an OEM or aftermarket alarm system. I believe both OEM and aftermarket systems has a trim pot to adjust the sensitivity of that tremor switch. Hope this helps ......