Makes lot of sense.... moving the central heating from a fused connection unit (FCU) to a plug and socket so it can be powered from in inverter and batteries does make some sense.
And once you've a plug and socket, you can use a plug in power meter to see how much the oiler used.
For power management, you could run the boiler for (say) 10 mins every half hour to heat the rads. That would make your batteries last longer.