Will add my two-penneth too.
We have a large 4 bed ex-council house in the middle of the countryside - it is the end one of 6 with single skin walls (no cavity) and big windows which at least are double glazed. We inherited ancient storage heaters which were more or less useless, a firred up water tank with immersion and a rayburn which only worked as an open fire. To put it bluntly the house was freezing in winter except for the lounge and the electric cost us a fortune. No gas in our village and reluctant to install oil due to costs and upheaval. Downstairs is open kitchen/diner/lounge. We went for the following solution.
1. Small central heating system upstairs with an electric central heating unit which runs up to 8 radiators. We have radiators on landing, hall, 4 bedrooms and bathroom plus one in dining room.
2. A highly efficient water tank which is linked to the heating unit - this currently comes on for a hour between 6-7am 4 days a week and this provides enough water for 2 of us to shower all week. We usually need a couple of extra hours when my son is home from university. The water-tank can also heat directly from the electric with an immersion in the tank and it also has the option to connect to a solar panel later if we decide to invest in one.
2. 10.5KW Hunter wood burner with door on both ends - we opened up the chimney breast on both sides so that the burner faces into dining room and lounge thereby heating our entire ground floor living rooms. We looked into having a back-boiler for the heating but this would have meant we couldn't open up the chimney breast on both sides.
Also - we were advised that if we had a back-boiler the first hour or two of heat generated when we lit the wood burner after work would be diverted into warming the central heating system so the effects of the wood burner in the living rooms would take a while to work. With an independent wood burner the heat pumps straight into the room - which it certainly does! It seems that back-boilers are good if you can keep the wood-burner fed over longer periods of time - but if like us you get in from work about 6pm most evenings it would feel like the room just got warm before we headed for bed!
We are also lucky that my hubby is a gardener and all wood that he removes from gardens make it back to ours for our wood pile - we managed to get through all of last winter without actually purchasing any logs! However, the heat output is not always as good as with well seasoned logs - but it's free so who's complaining?

Donna