The usual arrangement is one thermostat in a hall, an underfloor manifold with all its loops open, and radiators upstairs on nothing but their own valves. So the hall decides the temperature of the entire house. The hall is also the coldest, draughtiest, least occupied room in it, which is why the bedrooms end up too warm and the kitchen never quite gets there.
The fix is not an app. It is zones. Underfloor loops get a stat per room, the first floor gets its own zone, and the two circuits get the flow temperature each actually wants — because underfloor is happy at 35 and radiators are not. On a manifold that is a blending arrangement, and it is completely routine work.
Then weather compensation on top, which is the piece that does the most and gets talked about the least. An outdoor sensor, a compensation curve, and the flow temperature tracks the weather instead of blasting at a fixed 70 and cycling. On a big house with a lot of thermal mass in a screed floor, that steady gentle input is exactly what the building wants — it is the difference between a floor that holds a temperature and a floor that lurches.
And because so many houses here are heat pump candidates, this is not optional detail. A heat pump on a fixed high flow temperature with an on-off stat is a heat pump running like a bad boiler. Get the controls right first and the heat pump conversation gets a lot shorter.
