"Hardwoods too expensive so we get spruce in a forestry lorry, which keeps tarring up the inside and appears to provide f* all heat. Needs chainsawing, barrowing, splitting, stacking, drying, restacking closer to the boiler then finally burning. And it just chews through wood for very little result. In Feb I weighed each log that I put in and it turned out we were burning 50kg per day, and if we wanted water hot enough to shower in it needed more. Sustainable it ain't..."

Yea...we've run wood a few years. Were promised it was going to be hardwoods...but found a sneaky amount of birch & spruce appearing in increasing quantities and as you say, the volume you go through is phenomenal.

The only ones I have seen worth having for wood are those with a secondary burn. A friend had one & burned mainly scrap from the joiners in it. Gave a decent heat output and was economical enough not to be running out to the woodpile every five minutes.
The "large, efficient internal wood burning stove, maybe connected up to a smaller boiler..." Is essentially our setup. I have one inch pipes running up convection-wise to a coil in the tank above with electric backup and 3/4 to a pump and radiators. Been working 2O+ years now without a problem, so not bad for a self-installed system. We were also lucky that the fireplace wall was built when the farm was war-requisitioned as they made it with sturdy engineering bricks from the local pit so we didn't need all that chimney lining malarky... and thus the surplus heat goes into the solid wall acting as a huge storage heater.