heads up, on boeing 747's Ive sleep in a bed, normally theres a couple at the back of the plane in a room up some stairs.
Check the doors out, they are usually locked but you might get lucky. You'll get told off by the flight attendant if they catch you but I managed a ~8hr sleep on one flight (certainly better than trying to doze on your seat).
I think they have this room for a sick passenger or if they (attendants) want a kip.
All transoceanic flights require crew bunks for crew rotation.