Nest Again Sorry

[stem]

Bad connection somewhere maybe?

The Heat link terminals are pretty fiddly even for those that wire them frequently. It's easy to tighten the screw on to the insulation and not the conductor.

 

[billsy]

OK all sorted. He told me he needed to re-connect the thermostat wires that we had re-utilised for the 12v line, to keep boiler happy, and then bridge the live switching terminals at the thermostat. Stem you nailed it in your first post.
Just means I need to buy a 12v power supply to chuck in the wall to power nest stat. No biggie.
Thanks to all.