If there's an isolation valve on the hot water system where would it be?
(it's a boiler connected to a hot water cylinder with a heat exchanger, so the boiler including radiators is a closed system and the hot taps are driven from the tank). Perhaps there's something at the outlet from the hot water cylinder? (which I haven't checked as it's hidden behind a wooden panel)
If there's an isolation valve on the hot water system where would it be?
(it's a boiler connected to a hot water cylinder with a heat exchanger, so the boiler including radiators is a closed system and the hot taps are driven from the tank). Perhaps there's something at the outlet from the hot water cylinder? (which I haven't checked as it's hidden behind a wooden panel)