Roland Perry wrote:

Andy Burns wrote:

https://www.thefloorheatingwarehouse.co.uk/acatalog/info-Slimline.html

Could I wire that with one pair of conductors to the boiler?

No jut two wires, it'd need a 3+E cable (perm live to stat, neutral to
stat, switched live to boiler, earth)

How is it powered.

mains

The site above has very little [actually, none] installation
detail.

The heatmiser site itself has install manuals, the only reason I linked
to the website above is that it's £20 cheaper from there.