If they go out of business, they won't have any money to return to us. I don't suppose they have kept our money in a segregated client funds account.
So, in that unlikely event, we would be claiming money from the liquidators (there won't be any money) or from our credit/debit card providers (which will work, or not, depending on the Ts&Cs of those providers, and the laws of whichever countries we happen to live in). So let's hope that doesn't happen, then.