On/Off control is the method of control used by most heating systems in the UK. The controls simply switch the current supplied to the boiler on or off at different times.

The Y6630D is a battery powered Wireless Room Thermostat and mains powered HC60NG Receiver Box, pre-bound to give intelligent room temperature control of a single zone. It can be used in conjunction with the Sundial Y or S Plan or as a stand alone device for room temperature control of a combi boiler system. The...
The T6360 is a mains voltage Room Thermostat designed to give automatic temperature control of domestic wet central heating systems. It can be used to directly switch a circulating pump or boiler, or to operate spring return and motor open/motor close zone valves.   The T6360 can switch electrical heating loads...