Cracked on and all seems to be working as normal. I didn't blow up the kitchen (or a fuse)!
Thanks for help,
yep, the neutral is capped off inside the boiler so is just running live
Set-up seems similar to that posted on this video (eg no earth wires and no neutral into boiler) …
The other end of the black sheathed wires are deep in the bowels of the boiler! No idea why it wasn't attached but boiler has been working so far...
Rolling up sleeves and installing the Nest thermostat we treated ourselves to for Christmas.
Attached some screenshots of previous and new wiring...
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