Quick update on this situation...
Hari very kindly helped me out with getting my Zwave controller and remote sorted, and we managed to add the non-responsive light switch, so I am happy that everything is set up the way it should be on the Zwave side.
However, seeing same problem with the door/window sensor. According to the Zwave logs, moving the magnet away DOES provoke a response, but alas the alarm does not sound. If I pick up the sensor (i.e. activate the tamper switch), the alarm sounds.
Hari has speculated that it could be an events problem, but I have no idea where to go from there. Seeing as the tamper switch sets off the alarm, and the Zwave logs shows the magnet as working, I am really stuck.