I'm about to have a run over the Atlantic and for the first time want to use my laptop to work/watch movies. Usually I fire up the laptop to recharge my iPod and then shut it down so there's no real worry about battery life but on a 10-hour flight this time I intend to use it for the majority of the time.

As such I've got myself a seat with a power socket (flying coach, American, 777) but am not too sure what to plug into it. I've found a 75w invertor at Maplin in the UK which should do the trick but I'm not sure. Can anyone advise?