Replace Honeywell CM927 CH controller - help

Hi all. Sorry if this isn’t the right place for this (although I think it might be).

I’ve got a HA Green device with the intention of controlling the central heating with it. My CH is a really old Honeywell system, using the CM927 controller. I can only find a couple of posts about this on the forum here, with one from 2020 that suggests that what I want to do should be possible. I have got the ZBT-1 dongle which I think is what I need for this, but I’m not sure where to go from here.

Any help, pointers, etc would be really appreciated.

TIA