Thanks to Paul and Liam for your comments about the ventilation - I shall check that out before doing anything drastic like drilling holes or buying stuff. Paul - I'm afraid there already is a vent in one of the doors... so maybe that will help.
Turning to other BSS considerations, yesterday Jim put up the heatproof board behind the stovepipe, and on the side of the cupboard above the level of the stove, where I'd noticed it getting quite hot in the winter (before I'd got the hang of controlling the stove properly) although it never actually scorched, it was hot enough to worry me.
The board at the back is covered by the sheet copper recycled from the Ely chimney hood. It's worked really well, utilising the angled bit that already existed - there was even space to slip a strip of board inside it - to cover the join over the framing. At the moment it's fixed with those special sharp screws, as it's into oak, but later they'll be replaced with nice brass ones Part of my yesterday was spent in polishing it all up - now I have to keep it that way. If I remember rightly, copper polishes more easily than brass, but tarnishes quicker too.
I also cleaned and dried out the hold (again) and the engine room, and at half past nine last night finally got a third coat of paint of the engine room baseplate. Today I think we will do... painting.