Just a quick update on my progress.
I’m still bench testing the panel at this stage as I haven’t had time to install it. I was keen to see the delay betwern the DSC zone triggering and an esp8266 receiving a message on an mqtt topic. The esp8266 is simulating a relay or zwave lighting controller. I’m pleased to say that there is at most a 2 second delay. This confirms that the passive infrared motion sensor connected to the DSC panel will make a suitable room occupancy detector.