Sorry I haven't been getting notifications so I'll answer each point;
Sixwheeledbeast: No, it can't be. Maybe I've not been clear there are 4 PIRs and one door sensor. Each one has a 6 core going into it, they are not daisy chained. Into the control box is a 6 core from the bell box. And a second 6 core which brings in the 'switch' signal from each sensor on a single core, however I can only assume the other side of the switch is tied to ground or 12v in a mythical junction box who's location eludes me!
JMS: yes they must be jointed together but I have no idea where the