Got to replace a rad. Have switched off the TRV, but if I take off the plastic bit (to get a bit more room to swing the spanner), just leaving the metal valve fitting with the pin sticking out, is the valve switched off? (ie is that its 'default' setting?).
You can work it out by putting the cover back on and turning it off, seeing what happens to the pin. Most of them turn off by putting pressure on the pin to push it in - the opposite to what you were hoping.