Jaguar 23kW: Using hot water tap triggers central heating to come on?

When i use the hot water i then turn off the tap. About 30% of the time i find the central heating comes on. The hot water icon on the boiler is displayed (not the CH as is suposed to) and the burner lights. The only way i can shut it down is to turn of the boiler at the switch. Only after leaving it 15mins approx, can i turn it back on and the normal function icons are displayed. I have tried setting to holliday mode, reset button including turning combi on while pressing heating icon.