Winner of the best suggestion so far:
Separate thermostat set to 19 from 9 til 9, like @dangeourbrain says, but leave the old one in place (disconnected) to give people the illusion of control.
Good idea of a thermostat with an upper limit though, thanks @simon_g
@dangeourbrain: Sounds like you’ve concluded best option is heating on all the time during the day. Keeps the fabric warm and means not cycling hot /cold. But this would depend on how much the halls are used. Ours seem to be used about half the time (including evenings) so maybe not the most efficient as we’d be quite often heating and empty building. How much are your halls used?
Nest could be an option, but I don’t think there’s wifi. And I don’t think the lovely caretaker is a fan of technology, so anything too complex is out…
@mert
Yes, we had one at a place i used to use, and we have similar in some of our older meeting rooms/buildings at work.
set at (say) 16 when the button isn’t pressed and 19 when it is. And a two hour timer.
Sounds like it could be ideal – any chance you remember what brand it was or what it was called so I could look it up?