Millsy 82 I guess you haven't got an actual say on the situation (i.e. what one would do) rather than the initial installation that I had no control over
You were told on page 2 what the likely problem and cause and remedy was I would just be repeating what everyone else is saying.
Why did your OH say get a proper plumber from a company in? Surely the one who changed your rads was a proper plumber as well.