I cancelled my booking within the 7-hour free-cancellation period that my flight had when I realized I need a different flight plan. It's possible to do this online, even though Opodo says on some sites that you should call a hotline. Opodo refunded my money to the penny within 3 working days (only downside is that since my account is not in GBP I got screwed on the exchange rate, but that's my bank screwing me, not Opodo). One weird thing is that I still keep getting emails as if my booking was still confirmed and even when I log in to Opodo's site to manage my booking it still appears to be confirmed, only thing indicating a refund is that in the "Billing" section, the mentioned total is "Total: £0.00 Congrats! That's an amazing deal". Aside from this confusion, really good service.