Heating a home office

Electric storage heater(s) perhaps. Much maligned, but simple and cheap to install and very effective in well-insulated buildings of high thermal mass.

Night-rate electricity on British Gas 'click energy' 2-rate tariff is currently 2.091 p/kWh +VAT (Eastern region, price varies around the country).

Possibly, since your building seems to be well-insulated but low thermal mass. Supplement the storage heater with and electric fan, convector or radiant heater - take your pick.

Solar thermal with vast interseasonal heat store...

I'd think the reversible air conditioners that have been mentioned, presumably they become a better investment as electricity prices go up compared with resistance heaters.

Well the air con thingies will be most effective when there is only a small temperature differential between inside and out. A small wood burner for really cold days, mind ashing out can be dusty so computers' filters may suffer.

In your locale also consider a 5kW(t) pellet stove, there are some about used now. They're about as noisy as a standard PC, so not much good in a quiet domestic environment. There are a few associated problems but mine runs OK on 50:50 mixture of surplus barley or wheat and wood pellets.

AJH

No just the water vapour.

Thanks Andrew, and everyone else, for the responses. Most illuminating, although it was actually hot air I was after:-) Quick discussion with my better half pointed out the presence of an old, ugly but serviceable wood-burner in the lean-to. Provided I can get a cheap bit of chimney, I think that might be my answer...

In article , Andrew writes

Mind CO fumes with a too cheap chimney;!....