The cancellation window on Expedia depends on the type of booking. For most flights, you can cancel within 24 hours of booking without penalty, as long as it’s more than 7 days before departure. Hotel and car rental cancellations vary, with policies ranging from free cancellation to fees.
Source: https://bcpportal.bcpcouncil.gov.uk/forums/general-discussion/77e2dc65-dd9d-ef11-95f5-6045bd11e914