Energy Suppliers, Suppliers of Energy. Gas / Electric

I'd just assumed that regulators wouldn't allow them to given that their role is to supply an essential service

Nothing happens to consumers' supplies if the "suppliers" go bust, because the whole thing is fictional, so none of it matters. LOL or whatever.

I've submitted a refund request with Bulb for the credit I had, which they've apparently accepted, though I have a sinking feeling the money will be lost in the ether if they collapse before it gets to my bank account.

Here's the page they send you to when you email them, which I don't think is linked anywhere:
https://account.bulb.co.uk/dashboard/payments-and-statements/refund