Billy's accent
It's awful, what was Karl Urban thinking with that mish mash of cartoonish nonsense? Very irritating. It's like someone on a talk show is doing a humorously bad imitation of a cockney (or similar) accent.
Also he says to Hughie "Sorry I hit you, I lost me bottle". Losing your bottle means to chicken out, not lose your temper.
And is Billy's father supposed to be British? He has an Australian accent.