I added two radiators in my attic - the first rad is working fine and warms up however the 2nd rad is cold - (both have same fittings trv and thermostats). I swapped thermostats over but the problem remains. The 2nd rad is further away from the pipes that are coming from downstairs - I have checked for leaks and air - the 2nd rad contains water because I bled the rad to remove air. Should the hot pipe running to the lockshield valve on the 2nd rad be warm? Could there be a blockage in the pipe to the 2nd rad? What have I missed and how do I fix this problem? (Thanks in advance).