Hi,
One of my rad stats has stuck shut so have cold radiator. Looking at previous posts on this site, you can unstick it by "pulling up pin with a pair of pliers".
Looking at mine, if you prise the plastic top off the control, there is a chrome knob about 12mm in diameter, which you can depress & it bounces back up. Is this the pin? Not sure of make but says Concerto on control.
Any help appreciated - I'm not competent to drain system & muck about with it, but if there's a quick fix I'd like to know!
Justin