Stella Z: how to set thermostat mode in Lua?

[p0puptoast]

I am trying to set the Stella Z thermostat mode in a Lua script but I am failing.

Looping through "deviceName,deviceValue in pairs(otherdevices)" shows that the stat mode devices have a nil string when the dashboard shows that there is a setting, and attempting to set the stat mode device value itself seems to fail as the dashboard value stays unchanged, even after a wait, so that's incorrect.

From the Stella Z manual I can see:

Switching between the four modes is accomplished using the Z-Wave command classes 'Thermostat Mode' and 'Basic'. The following mappings apply:
Frost Protection: BASIC SET 0x01, THERMOSTAT MODE SET 0x00
Energy Saving: BASIC SET 0x00, THERMOSTAT MODE SET 0x0b
Comfort: BASIC SET 0xff, THERMOSTAT MODE SET 0x01
Direct Control: BASIC SET 0xfe, THERMOSTAT MODE SET 0x1f

Just a little bit more info in the manual would have really helped: I can see the use of UpdateDevice from other scripts e.g. commandArray['UpdateDevice']='idx|nValue|sValue' but which value do I use to update the device, and am I trying to set nValue or sValue. Obviously the listing above from the manual lists two values: how do I use those?

I have read z-wave descriptions online but a lot seem quite vague: it would be really useful to read exactly what supporting a particular command class includes.

Dave