Ok so here are the planes (according to seatguru):

LON - EWR = 757-200, so looks like free

EWR - PTY = 737-900 - which seems to all be converted to direct TV, which seems odd if it will only work for half the flight

AS long as there is something I'm not bothered, might just load up the ipod anyway.

And will make sure to bring that 2 plug adapter - I know I have one somewhere...