My system has started playing up. We noticed it when the weather turned warmer, and we turned the heating off. But the heating stays on regardless even if we also switch the water off at the timer (a Honeywell 7 day water and heating model). Basically, the pump continues working and the boiler fires up. The only way I can get things to stop is to turn the timer off at the mains. I have disconnected the frost stat to no avail, so that can't be the problem.
Any help would be appreciated. Thanks