Welsh Sphagnum harvest does look to be sustainably and responsibly done, judging by a recent report commissioned by NRW. I would imagine Big Moss comes from further afield - Eastern Europe or even Southern Hemisphere - does it say?
Babyllon are based in Northampton, but there is no mention of where the material is sourced. I was tempted to buy a bag to see what species I could identify, but decided against it. Could to know that it can be harvested responsibly.