I have a Ideal Isar H35 combi boiler and have had a problem with the radiators being warm intermittently even when the timer is switched off! I've spent ages researching this and experimenting and have decided its the diverter valve within the boiler thats at fault. When the boiler ignites to heat the water (showing 't' on the display) a small amount of hot water is escaping into the radiators and heating them! I'm a single mum with very little cash so this is scary stuff!! Can someone please advise wether I need to replace the valve in its entirety or just the cartridge?? How much should I expect this to cost?? Any advice gratefully accepted!!!