I recently bought a Horstmann C27 Programmer and Digital thermostat. I installed the C27 and it worked fine. I then installed the thermostat and stupidly guessed which neutral wire to stick in and guessed the wrong one - resulting in a pop and untimely death of my C27 programmer.
I then got the correct wiring for the digital thermostat and the electritian who fixed it used a workaround on the backplate wiring so that both hot water and heating switch on from the switch with the expectation that I would move a couple of wires (I'm sure I've got this right) and plug in my next door neighbour's heating clock temporarily when I borrowed it.
Here's the problem. It works on his but not on mine, despite everything else, incluing new thermostat, working from the switch! Anybody got any ideas?