I looked into this before buying an AZ ticket at the time the survival of AZ was in the air and it seems that UK legislation is better than that and puts the credit card company in the shoes of the defaulting trader, which would mean that you could insist on the credit card company taking on the liability ot providing you with the flights (since the airline would have that obligation).

I did not have to test it out since AZ kind of survived () although my guess is that you would have to have a tough fight with the card issuer if it came to that. Not sure either whether the legislation protects you to the same extent in case of partial payment with a credit card (which would be the situation for a redemption ticket).