Consider a heat pump

Set heating timers and schedules

Heating an empty home wastes energy. A schedule makes the heating come on when you need it and go off when you don't.

Reduce your combi boiler's flow temperature

Combi boilers run in their more efficient condensing mode when the water they send to radiators is cooler.

Turn your thermostat down by 1°C

Lowering the room temperature by a single degree reduces how hard your heating works, and most people barely notice the difference.

Fit thermostatic radiator valves (TRVs)

TRVs let you set each room's temperature separately, so you stop heating rooms nobody is using.