Perhaps my question wasn't very clear.
Your thermostat interprets commands sent over Zwave and modifies its settings (example heating termperature setpoint) accordingly. The means by which it interprets those zwave commands is what I am questioning, and is irrespective of the Zwave controller.
The zwave controller manufacturer will not be able to help me with this and will refer me back to you.
Please tell me if there is a way to change the behaviour of the CT100 so that it interprets temperature setpoint changes received via Zwave as degrees Celsius as opposed to degrees Fahrenheit (note that I'm not referring to the display units which is a different matter).
I'm not very knowledgeable about how these devices talk at a low level, but I'm assuming there is no unit (Celsius/Fahrenheit) supplied with setpoint commands by the controller, just a value, and that it's up to the thermostat to interpret it as Celsius or Fahrenheit (obvious design would be to decide this based on the unit that the user has chosen to have displayed on the LCD of the screen).