Is it OK to store down sleeping bags uncompressed in an airing cupboard? Just googled it and cannot find anything to say whether it’s OK or not. Any advice much appreciated. Thanks

Yes.

Most decent ones come with a large storage bag, either mesh or cotton

That’s the way I store mine, loosely bundled into a cotton bag that came with it. How would it be a bad idea?

Provided it’s dry and not compressed, go for it.

Mine lived in the attic in their mesh bags.

Big mesh bag that came with it for one and other one is in a large cotton bag. As far as I’m concerned it just needs to be stored lofted, in a bag with a closure to stop moths getting in, in a dry place.

Mine came with mesh bags but I just stick ours in the unused suitcases which also like dominant in the loft

Mine live in the empty suitcases and under our bed.

Your suitcase dominates your loft 😯