Thanks for that Tony. Since posting I have talked to a heating engineer who suggested checking pump by unscewing centre nut and inserting scewdriver to see if pump is acually running. He thinks symptoms suggest that pump needs replacing. What do you think?
Trevor
Central heating upstairs works fine but downstairs fluctuates-but mostly cold, even when stat temperature has not reached setting.
I turned the radiator valves off upstairs and the downstairs heated up.
I then opened the radiator valves upstairs and all worked, but noticed same happened...