Looks like I need to do sort an air lock in the central heating system. System was drained down twice when we had bathrooms done up. Now looks like the plumber didn't bother his @rse to actually check all was ok. Got two cold radiators at the other end of the house upstairs. Did bleed a fair amount of air out of the others and had to top up the system. Oh well that`s what I`ll be doing this afternoon.