But in what way are those carbon neutral? (which is what I thought was the point of this entire thing)

And that doesn't answer my questions.

It wasn't supposed to do so, but raise awareness that your questions are already highly relevant in the present and not just a hypothetical future: The UK consumes something on the order of 8 million tons of wood pellets per year.

The carbon footprint depends on the source of the wood (eg replacing naturally grown with farmed trees is not a carbon neutral activity). Shipping has to be considered as well.

Uninformed layperson that I am, I'd guess power-to-gas would be a superior solution, but it's pretty expensive right now...