Having used Opodo a lot in the past without issue, my last flight booking turned into a nightmare....
All booked, a few months later I get an email to say there is a major schedule change and please phone them on the number below (first failure, the email had no number in, no number found on their website - eventually googled it).
Long story and 6 calls later(and them not returning calls when promised) I'm told the airline has reschduled the flight (not cancelled it) and because I'm not willing to travel 3 days either side of my date I'm not allowed a full refund. So the airline gave me back only part of the cost, and Opodo charged me £25 per person to cancel the flight! So from a £600 flight I'm nearly £200 out of pocket because the airline can go change the flight to up to +/-3 days from the original booking date. So angry, and Opodo don't have to charge that £25 per person cancellation fee - but they decide to. Awful customer service and don't believe in trying to keep the customer happy. Making money out of the customer when the airline has messed up.
STAY AWAY!

An update...so having posted this message Opodo did refund the per person cancellation fee. So that is the good news. However, even now, months after the flight was "rescheduled", if I go into my account it still shows my original booking as "confirmed" with the original flight times (even though I have cancelled it and the flight isn't going on that day/time). So if I had never seen there email about the reschedule I would happily be assuming the flight was still running (probably right up until the moment I try to check in). So this gives me no faith in any information their website is reporting about any booked flights.