I've got a CH system with thermostatic valves on all radiators including the hot water tank (which has a copper sensor from tank-body to valve) - I think the bathroom radiator also acts as a bypass. So presumably the only mechanism for switching off the boiler is the boiler stat? Is it risky or dangerous to be entirely reliant on this? Could I introduce a room stat and just set it a bit low with the thermostatic valves in that room set high? And similarly with the hot water tank?