Well, you need to remember that for all practical purposes you're flying from Gatwick to Houston, not Orlando. That's what all the screens and information will say at Gatwick. Also, you will clear US immigration and customs at Houston, not Orlando. The Houston->Orlando flight will be a purely domestic flight.

You can't check-in online with CO at Gatwick so this itinerary will not work even with cabin baggage only, and even though you don't technically need to clear either UK immigration or UK customs at Gatwick if arriving from Cork. You just don't have enough time: 15 minutes from arrival time of your Cork flight to last check-in time for your Houston flight is just not enough. You will need to change your Cork-Gatwick flight to one the day before, and find a hotel for the night.