you will find that most hotels nowadays in cork or anywhere else will let you check in early without any prior arranging. I have found that if you arrive say at 12 midday, they will let you leave your baggage if there is to be a delay but rarely will you find they cannot give you a room earlier. When you arrive at your hotel, just be very very very nice, ask if you can check in early and if not that is perfectly fine, go have a bit of lunch or what ever, you wont have to wait long.