for now, with the power off, the pumps dont run. The only problem would be if a power cut occured towards the beginning of a furnace burn after the boiler water has got to 75 degrees and plenty of heat still to be collected from the uncontrolled burn – the risk is that the 200L of water in the boiler gets above 95degrees. All the safety systems would kick in. However before that, assuming Im around, I would douse the fire.
A power cut in between burns would just mean I dont use the boiler. Hot water in the thermal store would provide DHW for a few days. I would turn CH off and just use the two woodburners for heat and the one in the main room for cooking on.
Longer power outs and I would rig up the inverter/leisure battery system with periodic recharge from generator sessions.