Thanks cordelli, lots of useful information there .

Sad to see Newark at the bottom of the list for 2011 but I guess it just revolves around what the weather is like, if the weather is fine in both London and NYC on the 14th December then I can't see there being major delays.

Agreed about the customs and immigration though, apparantely evening time is the most busy, I've been considering to change my usual seat the back of the aircraft to somewhere closer to the front to disembark faster but it wouldn't really make that much difference overall unless I was bringing a carry-on only and not checking luggage .