We have two now only decorative coal fires in the house (I mean that they might be functional but we have no intention of using them & would need to the chimneys inspected & cleaned). I've closed the flue hatch (I can't remember the right name; the metal flap you can reach up to by hand) over each one, but there are still drafts, especially when it's very windy.
What's the best way to plug them up & block drafts, but without making it too difficult for any future owners to unblock them if they want to use them? A big wad of rock-wool?
(So don't tell me to fill them up with expanding foam!)
Thanks, Adam