Firstly sorry for the delay in responding and a massive thank you for sending these Andy I will take a look through them over the weekend.
I have tested the ESP32 using the header pins to detect the alarm trigger and it seems to work fine. Powering it from a separate power supply for the tests. In the meantime I have built out the software so now have a mobile app to manage alerts / control it/ alert user etc. as well as all the user management to enable multiple users, multiple detectors etc. The ESP32 also fails back to the mobile network should the internet be down etc. Whilst I built this for my own use/ enjoyment, although not my original intent it is probably close to being something I could sell to others. Wonder what the market is like :)
Once I get it up and running I might look at interfacing with the other header pins particularly on marked as "set" in the documentation so wondering if that enables remote set/ reset or maybe just triggers when the alarm is set by the user.
Many thanks again
Lee.