This is a little complex... My heating is from oil boiler. Only can get hot water if heating on and vis versa. In the summer just turn it all off. Now I was thinking about what is causing it...read about might be micro switch, could it be the timer wired wrong? But....I don't really use hot water. I have no bath, I live alone, I boil a kettle twice a day to wash up..... Rather than having a boiler technician investigating a friendhas suggested that I have two valves fitted to stop water going in or out of the water cylinder, effectively isolating it so I don't have it heating, which is what I'd do if the switches worked anyway.is this safe?