You said it, very lazy

I’m not familiar with how the UK decides on dispatching order for power plants, but if they follow a similar protocol as the US where is a combination of marginal cost and emissions, I wound in then expect that the bio-mass plant (with lower expected emissions) will be dispatched more often than the coal fire power station.

That would significantly affect the emissions/kWh

Finally, like you said we would need the transportation emissions and I would ask too for info on whether the source of the wood is a sustainable managed forest. If it is, that wood has near zero emissions as the forest regrows (except for processing emissions)