Today we got the boiler fired up, and the heating running on the first and second floors. There's still more to do on the plumbing, but it felt like a major milestone to actually heat the place up! I intend to give it a longer run tomorrow to see how the building envelope performs in terms of heat retention.
A fuller write-up of the heating system eventually used to follow in the next few days. For now I'll summarise - we've used a Worcester Bosch "system" boiler with floor-by-floor programming of heating times and temperatures, and an external weather compensation controller, together with a Navitron 250 litre cylinder which will supply hot water in conjunction with the solar thermal collector (this part still to be done). Here's a recent photo showing the boiler install in progress:
Other trades have also been progressing - second fix electrical and joinery, etc.