5) The alarm went off while I was about to fill the car with fuel, not sure why
This once happened to me. As I unlocked the filler cap, I managed to press the "lock" button and my wife who was in the car, moved about and triggered the intrusion detector.
I can also recommend the pump method for oil extraction (assuming you have a CRD). The engine was designed with this in mind. Oil and filter can be changed from standing position in front of car. No crawling underneath required.
Maybe your friends prefer to be inconspicuous by driving the ubiquitous European offerings?