'tis your own money to manage at the end of the day, and far be it from me to be talking like I never made a poor gambling decision when I do it regularly enough, but you were already in profit no matter what from Fact to File winning at Cheltenham.
My own mantra there would be to let it ride, UNLESS I thought Cork's price was too short. Laying off should always be about price and expected value rather than falling into the trap of thinking "I don't think they're going to do it". Maybe you did still think they were too short when you laid off, but if they win it outright you might end up thinking "Ah, I gave away almost 3k there".