I booked Easyjet to fly Rome to Sicily and canceled within 24 hours, but the cancellation fee was almost the price of the ticket. For 2 tickets to Palermo for $165, I got back only $14. When I saw that for the flight I had chosen it said "only 3 tickets left at this price," I booked it thinking that the 24 hour cancellation would be the same as US airlines and would not involve a fee, or that the fee would be the credit card surcharge. I had no idea it would almost completely wipe out my refund. Keep in mind that this booking was some 3 months before the flight making it almost certain that they will resell these seats.
Also, the only way to cancel within 24 hours is to call their customer service number in the UK. But the customer service number is answered only during regular business hours UK time not 24 hours. When I called them the day after during business hours, they did do me the "favor" of waiving the 24 hour deadline. Fortunately, I had sent them an email canceling the booking within the 24 hours. I had to get the email from a Google search as it is nowhere on the web site.