Hi Guys,
I have two simple heating circuits running off a thermal store; one is the UFH and the other a towel rail then radiator (in series). At present, the control for the pumps running is locally on the store and they are bimetallic thermostats (the old kind) which make the pumps run too long which is a waste of power and hot water (and cash).
I don't mind the set up as is as it's simple but need a much more accurate switch on/off stat. For example, let's say the rads are set to come on when the store temp reaches 40 degrees. I need a thermostat which measures when the water is drops below this temp (or whatever is set) that makes the pump stop running and not at say 30 degrees. The units must have probes which slot into tubes in the store. There is no control in any rooms, like I said before only local on the store.
Looking forward to your comments.

Thank you , Nick.

An NTC based thermostat should be a lot more accurate and have far less hysteresis than a bimetal. Not sure about brands, types, etc, I reckon there must be an analog version with tunable upper/lower temperature settings somewhere.
A digital solution would be even more accurate & versatile but probably OTT.

If you're concerned about wasting power/ hotwater/cash, youd be better putting controls in the room(s). Theres no point in even starting the pump if the room(s) dont need heat.