Hi - we have just moved to this house and all the radiators work fine except two upstairs in adjoining rooms that seem to be at the end of the loop. The pipes either side of both are cold and there is no air in the two radiators. They are fitted with thermostats and the inlet valves are open fully. Anyone have any ideas please? If it is an airlock in the pipes, what do I look for to draw off water? Many thanks - I am not a good DIYer!