I’d start by going directly to the airline rather than paying a claims company to do it for you. Under UK261, you can generally claim if you arrived at your destination more than three hours late and the delay was within the airline’s control. Submit the claim through the airline’s complaints or compensation page and include your flight number, booking details, and how long you were delayed. If they reject it and you think you’re entitled, you can challenge the decision and potentially escalate it through an ADR scheme or the CAA.