I'm no expert (commuting less than a year myself) but from what I've seen on this site as long as it's a good quality bike (ergo, not a Wal-Mart bike--if you have WalMart in Ireland) fit is the most important. You're going to want a backpack or pannier setup that makes you comfy, loads-o-lights & reflective gear, a comfy helmet, and weather appropriate clothes.

40 miles is a long way to pedal if you're uncomfortable.

Good luck and keep us posted!