Thanks @mark.cockcroft, I've implemented all that I found in your code as well as the attribute declaration, most of the functionality is working but I can't get minHeatingSetpoint / maxHeatingSetpoint to work, when I go in to Google Home, the lowest I can go is 9°C yet I'm asking it to me able to get down to 1.5°C (I might try 4°C tonight just in case it's outside it's hard limits).
I will also try removing the thermostat and create it again and see if that helps?
I found this other thread that I missed before and found pretty much the same info also.
