Flightmapping - if the total value of the transaction was £100 or more, the consumer credit act will apply and a refund can be had from the card issuer. With debit cards, you'll be relying on anything you can get from Duo.
Amex issue both charge cards (no chance of refund) and credit cards (see above). You need to check which one you have.
You'll need to check the T&Cs of any travel insurance, as cover will vary by policy.