It's 15 in the UK and 18 in Ireland. Interestingly enough, I just bought that film on DVD last Saturday.
Anyway, some other examples of films that have different UK and Irish ratings:
Die Hard 2: UK 18, Ireland 15
The Specialist: UK 18, Ireland 15
Blown Away: UK 15, Ireland 18 (because the film's about an Irish bomber)
A Bug's Life :UK U, Ireland PG
Toy Story: UK PG, Ireland G (equivalent to U)
The Cider House Rules: UK 12, Ireland 18
Garden State: UK 15, Ireland 18
Charlie's Angels: UK 15, Ireland 12
Happy Gilmore: UK 12, Ireland 15
Midnight Run: UK 18 (was originally a 15), Ireland 15
The Devil's Own: UK 15, Ireland 18 (same reason as Blown Away)
A Dangerous Man: UK 18, Ireland 15
Stan Helsing: UK 18, Ireland 15
The Ricky Gervais Show - Dolphins: UK PG, Ireland 15