It depends on the following:-
a) Which Airline
b)Which Departure Airport
If it is BA or Delta B767 300ER series then sorry to say but World Traveller (Economy Class) does not offer individual seat back TV, only the main central screen, it also does not show progress maps the one that tells you where you are, what time you wll arrive there etc etc.
Can I suggest if it is British Airways I would fly from London Heathrow Terminal 4 on the B747 400 or B777 which are nice aircrafts with individual seatback TV.
Good Luck.
Normally there is always strong headwind Westbound accross the North Atlantic which maens longer flying time maybe 8 or more hours depending on weather conditions.