Great tutorial @steve.maddigan. I think I might add this since I can't find a way to change the geofence in the home app.
For those using HomeKit, I've been using the apple home app for presence detection using automations in a very similar way to how OP has set up Locative. The nice part is I don't have to confirm running the automation when I arrive and leave, it just happens magically in the background. More info on that topic here:
https://community.hubitat.com/t/arrive-home-iphone-presence/104581
