As much as they sat the lines close at about 10pm, phone just before or even after. You then get put through to the American helpline, and they're usually better.
Had to do this twice, once for a dodgy update and another for RROD. Spent two hours on the phone in the afternoon trying to get them to understand, finally gave up then. Tried again after 10, and got it sorted in less than 5 minutes.