I don't know about luggage storage facilities, but if you can find them, or check bags through (have a small piece for changes), then do so.

Its only 5 hours, but you can certainly get some good grub (how adventurous?) by finding a few different places with a few different foods and eating. mmmm, top it off with a drink maybe at the Trident Hotel or something near the airport?

Vague? Yes, but an idea. You could also go shopping.