You could fit a shelf a few inches above the radiator to deflect the convected heat away from the wall a little, also its worth getting a long handled bottle bush to remove dust build up between the convection fins and improve the heat output.
Like S.P.S said has it been like it since new cylinder was fitted as could be a peice of foam insulation that was in the cylinder and has found its way into the smaller pipes of your bi-flow mixer tap
If your electrican confirmed that 240v is going to the motor but the valve is not driving open then you can change the complete actuator without having to drain down.
Im glad to be retired from it all, looks like your being asked to walk through a mine field wearing a blindfold with your fingers in your ears for good measure, good luck with that.
Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.