I have an unused Granary for conversion to residential. It is a mostly
redbrick and grey stone construction. It is within a 'quadrangle' and has a
river pretty close by (10m) on another side; not alot of space around it!

Given it will have the current levels of insulation installed, heat loss
should be fairly low, although very likely not as low as a modern build
construction. I am likely to go with UFH on the ground floor throughout.

Siting a gas tank could be do-able although it would have to be some 30-50m
away, and require digging up the yard for pipework etc. An oil tank would be
more tricky due to the nearby watercourse etc, probably a no-no.

There is a large expanse of roof, so some solar panels for secondary heat
would be a likelyohood.

So, has anyone real life experiences of using Air Source HP's, both in terms
of output, useability, install and run costs compared to oil/ gas etc?

I have 3ph available.

Your thoughts thank you gentlemen.

Tim..