FWIW I think I have found the best use of Smart TRVs - I was finding the "over engineering" of them trying to hit a temp was causing balance issues, so I now have a pseudo "on-off" setup:
Rear bedroom is indicative of how the other bedroom is setup too; but basically in the morning it allows heat from 0630-0700. The TRV needs 5 minutes to open so the first 15 mins are just a buffer.
Hot water comes on at 0600-0700 and is demanded driven depending on how much water was used the day before.
Heating is scheduled for the morning only - and as the upstairs gets warm first but is then mostly unoccupied, it only allows 15 mins of heat. It then forces the water downstairs which means the rads downstairs warm up faster than if both upstairs and downstairs was open.
The rest of the day if the heating is boosted, it just does the occupied spaces. However I have found an oil filled rad + ceramic heater fan are much more effective as only 2 spaces need heating. Then when the little one comes home, the heating gets boosted and her room heats up and retains the heat pretty well till the next day:
As you can see, it heats up in the evening when I boost the whole house, and then turns off until it is allowed to heat up again at 1630 and the heating is boosted again. It then gets 15 mins of heat in the AM to take the edge off before stopping flow to allow downstairs to heat up quicker in time for breakfast.
Costs:
Edit: This is KWH usage. The boiler is a 22KWH boiler so looks like it is modulating its gas usage: