Right, I've started to knock up a quick plugin based on the API at https://github.com/watchforstock/evohome-client.
It is purely in Alpha stage, but it takes your auth details then pulls down your zones, temperatures and setpoints and creates devices for them (with temperature and setpoint as states).
They should display in control pages and function in any regular 'if device state....' wherever the UI allows.
There's one action that refreshes the data when you execute it.
If you see an error in the log saying "No JSON object could be decoded" just execute the action again (or reload the plugin) - there seems to be a timeout with downloading the data so sometimes it fails once or twice then works the next time.
If you want to try it, do let me know if you have problems. It does need tidying up, and the other features (update setpoint, backup/restore schedule, quick actions) adding.
https://www.dropbox.com/s/fb3sbt49hfvj5 ... n.zip?dl=1
Peter