Heat store is a 205 clip top drum very well insulated and in the engine bunker, which is predominantly underground, and insulated. The boiler is also in the bunker so the bunker is always warm. The heat store goes up to about 55c the boiler then goes off and then the heating runs for a couple of hours till it drops to 40c and the pumps switch off. This is not the only heat we have in the house and cabin, just background.
The bio for the boiler is not very pure with a 5/45 fallout of around 2. I have run it on a mix of bio and oil and it is fine but needs cleaning much more often. I have a heater on the nozzel that gets it up to about 60c before the boiler fires.