Drayton Digistat 1

[Plester]

My flat has 6 Drayton Digistat 1 room temp controllers, each connected to a hot water valve, which in turn is connected to its underfloor hotwater heating circuit. All 6 hot water valves stay permanently open and are not controlled by their Digistats (which have functioning batteries and display temp). What is typical wiring diagram for such an installation? Are there typical reasons for non-function?

[buildersmate]

If the system worked in the recent past, and suddenly all valves stay open, irrespective of what their respective thermostat is showing, the fault is generic, and won't relate to the thermostats themselves.
You make reference to batteries, so it seems you have the wireless set-up.
There will be a wiring centre within the system, that connects to the pumps and valves, and fault is here, possibly nothing more than a fuse.
In my experience the controls valves are typically "normally closed", that is, with no power applied the valves do not pass water. You haven't got that status as the valves are open all the time.
It is a simple job for an engineer like me to faultfind using a multimeter, but there is little more diagnosis I can do remotely.
You really need a technician familiar with UFH systems. They are generically similar but not all identical.