Hi
I've used them, only found them in a small size - and yes, found out the hard way that if you use them to store small amounts of seeds, nuts etc, they do turn to confetti.
Also think that for long term freezer storage, they are not strong enough, got freezer burn last year on peas and broad beans. Went back to ordinary this year and it didn't happen
I did find some potato starch plastic containers in Lakeland though.
Now try and collect any plastic pots, containers that can be reused - Very annoying though when manufactures don't use plastic lids, best ones are ricotta cheese tubs.

Also found greaseproof bag type things in Lakeland so if I've made something like bread rolls or muffins, can put them in the bags and then only use one plastic bag to keep the lot in. Can then add greaseproofed bag muffin or roll to packed lunch and put used bag on the compost heap.

You can also get recycled aluminium foil which is another alternative, that can be endlessly again when used or if still clean reused.

Sue