i recall a pilot-friend's concern at the standard irish farewell of "good luck". apparently it leaves flyers westbound onto the ocean wondering what controllers know that they don't....
LOL yeah I know a lot of Irish controllers who say that, and I've even heard a few say, "contact the big boys on 124.7 adios!"
Heard that on liveATC and at the local airport, all good fun! Thats the least formal handoff I heard but the usual "slán" or "good luck" or the good old "bye" is what the Irish usually say from what I've heard.