My Jaguar boiler (24 KTVJ - on inside of cover) stopped giving hot water but the heating worked sometimes. I looked up and people suggested it was the diaphram in the diverter valve. when the engineer opened it up it was indeed torn. when we replaced it we realised it was the same valve used in the biasi boilers. it cost £6.50 and took 5 minutes to change. the valve is at the back, bottom, left hand. all water must be switched off. the diaphram is a round rubber plate about 10cm in diameter and sits in the golden round valve. you have to disconect the water connections to the valve and unscrew it out. once it in your hands, take all the screws of the valve and use a screw driver to open the valve in half. the torn diaphram will be in the middle. replace it and put everything back in place and job done. remember to restart the boiler by the main switch.
furthermore, these boilers are really rare and are i think made by Protherm. I have not heard of either before this.
furthermore, these boilers are really rare and are i think made by Protherm. I have not heard of either before this.