Both, thanks for the replies. I wouldn't be surprised if the previous owner installed it, as he was a retired engineer and I've already uncovered no end of bodgery in the house that he's put in.
I'm going to track back to the boiler and try and pull off a wiring diagram from the back of it, to...
All,
I've got myself into a pit of a pickle and after a bit of assistance.
Bit of a background, I've recently moved into a grade 2 listed Georgian priority with a number of foibles, but that is a story for another day.
The heating and hot water are via a boiler (old Ideal Mexico 2) and a hot...