If you can't ge the seat that ual747 is offering, i recomend 21J. I had this one when i flew JFK-LHR and i found it very very good. There was very little noise, and the turbulence was slim to none. Also, it was easy for getting off the plane later and it was a good spot because i was served i think 5th or 6th and they had my choice of meal
. Whatever you do, don't sit in the middle section, i hated that.