Thanks for the quick response.
It will be my first implementation of MQTT so I'm pretty much a blank canvas. I'll go with setting up the MQTT broker (server it's called now I believe) on my Raspberry Pi 3.
Installing OpenHAB2 on the Pi has been made a breeze by an unattended installer called OpenHABian. Bundled with the installer is an MQTT option which should set it up (it's accessed via a menu).
I'll be happy to share my lessons learned here, no doubt there will be a few
I've still got to order a few sensors and boards etc to get started so it will take a little while. That;s why I read this thread to get an idea of how the components all talk to each other. That would at least help me determine what I need to buy upfront so I can get busy with it. Any advice would be appreciated (just to get a motion sensor up and running)
I imagine it can become addictive!