I think this all needs a bit of qualification - everything depends on the heating requirements of your house and hot water consumption which in turn is greatly dependant on insulation/airtightness and hot water usage.
The biggest savings to be made will always be in reducing demand, particularly in the average UK house which is pretty bad when it comes to thermal efficiency. Anybody looking at reducing bills needs to address insulation else you are just pissing your money into the wind - literally.
We were in the position of having a house needing renovation, so spent extra on insulation - as a one off cost.
We now supply all heating and hot water from a high-efficiency wood stove & boiler combo tied to an 800 ltr thermal store. Heating is downstairs via under floor heating from the store and hotwater is via a coil in the top of the store
The house is approx 200 m2 (with slightly lower than average ceiling heights - why heat a bigger volume than you need)
The stove is 8 kw - 30% to the room & 70 % to the boiler.
Through the winter we average about 2 smallish builders buckets losely filled with well seasoned logs
The 30% (2.4kw) heat to the room from the stove - open plan upstairs of the house of approx 100m2 - gives too much heat needing the windows to be cracked open to give a sub 25 deg temp in the depths of the cold spells the last few winters.
We tend to have to light the stove for hot water only sometimes as the temperature in the house stays comfy with little input, although downstairs underfloor heating is always flowing up.
The advantage of the thermal store is that we only need to burn once during the day - hard and fast for max energy gain from the wood and minimum nasties up the flue to the atmoshere (dont underestimate the nasties, especially with more and more people burning wood)
The one off insulation cost was probably paid back in the first year or two in fuel savings. We have our own wood, but even if having to buy it in I think we would save money with this set up. We do have mains gas to the property, but dont bother with it except for cooking.