british gas wri receiver ?

receiver flashing red for hours.green light constant.hot water coming on fine.no central heating for a week now.new rechargeable batteries in thermostat.flame in thermostat flashing.wireless signal transmitting.turn thermostat up keeps going back to 19c.have a glow-worm condensation boiler.3 years old.have no boiler cover typical.never got round to itTOO LATE now.and its getting cold as well.