Hi Mark,
The plugin is really designed to control TRVs that are monitored via a remote thermostat. Typically, TRVs located ajacent to the radiators will have their temperatures affected by the heat coming off the radiators.
That's why typically the Remote Delta Max Value is set to say 5ºC so that the TRV doesn't switch off when the setpoint is reached on the TRV. So, for example, the Remote Stat is set to 21ºC and the Spirit TRV would be set to 26ºC (Delta Max = 5ºC). So the radiator will keep heating even if the TRV reaches 24ºC but the Remote Stat is reading 20ºC. When the Remote stat reaches it's setpoint, then the TRV is switched off (8ºC) and the remote stat is monitored and when the temperature falls beneath its setpoint, the TRV is turned on again.
Changing the design of how the plugin works could be a lot of work which I am unable to undertake at the moment.