Google for a salus st620rf.

Wire in the receiver onto the boiler and stick some batteries in the remote control unit.

You will need to remove the timer in the boiler as the st620rf allows you to have different temperatures during the day as it's a timer and flexible thermostat in one unit

And all your rads must have thermostatic valves except for one to act as a heat overrun bypass, usually the one in the same room as the remote control.