Aga with a combi boiler.

[oldbutnotdead]

Having the thermal store with the woodburner (and a loading valve to manage condensation issues in said woodburner) makes the system much more usable-without the store I had to be very precise with airflow and fuelling to keep woodburner at the right temperature so the radiators elsewhere worked properly.
My gas boiler runs happily vented or unvented so it (and the woodburner) are heating the store directly- the other option is to use coil(s) in the store so your pressurised boiler heats indirect. I'll dig the link to the bunch who built my store out-decent prices and options.
F and E tank for the thermal store- yes you'll need one, metal, at least 10% of the volume of the store plus rads, pipework etc.
Hot water-up to you, if mains pressure is good you can use either another coil in the store or an external plate heat exchanger- either way no header tank needed and no G3 installation either.

 

[oilhead]

I see I managed to add my comments to eric marks quote in post 13. My apologies eric. If you expand it you will see my thoughts.

 

[Keepflying]

FFS. Oil combis do not have a hot water store. Some but not all have a heatstore which is a small tank of PRIMARY water that is circulated through the DHW heat exchanger to give hot water on demand. Those that do not have a heatstore use the boiler heat exchanger for the same purpose.
Oil combi's are reliable, but like any boiler, particularly oil, require regular comprehensive servicing. The main problem with oil combi's or system boilers, is that the internal expansion vessel is insufficient for the capacity of the system.
In my opinion, trying to integrate cooking, water and heating among 2 separate sources is lunacy, and will result in even worse problems than you have with your combi. If you want to supplement your heating with solid fuel, then fit your multifuel as a space heater. If you still require the controlability of an automatic system, then you need a pressurejet oil boiler, (or install an LPG system).

You may wish to install an Aga type cooker with a boiler to feed an indirect DHW cylinder, but they take an awful long time to heat a cylinder; typically an Aga from cold with a 135 boiler can take up to 12 hours, as it 'loses' a lot of heat into the cooker.
If you find an oil combi unreliable, then the pandora's box of a double or treble integrated system an absolute nightmare, and finding someone to make sense of the installers works will be impossible, and they will have taken the money and run.

The oil boiler we have does have a small heat store built in yes and mostly works well, it just comes down to cost and the unpredictable break downs. My in-laws (who live with us) have it on a maintenance plan with Worcester but all the bloke does is come out once a year, give it a vac, fiddles about, moans about it and charges £50 a month. It still packs in annually with an ever changing faulty component leaving us without heat & water for a week at best. With 2 80 year olds in an old (& cold) farm house it's not good enough & I need to solve the issue. My initial thoughts were ground source but with the lack of insulation in the walls I have my doubts hence turning to wood fired as a solution, especially with the ready supply of firewood.
I'd never thought about splitting the load between 2 heating sources untill the post about the H2 panel above as was just thinking about an all new system from the wood burner that the oil burner could supply to if needed in the event of emergency (I'm ill or unable to chop wood for instance).
Be keen to see if anyone has any direct experience with the H2 panel?