I would take AA142 for the JFK-LHR ( dep: 0805 arr 20:25 ) for the most civilised eastbound option. No need to worry about sleep on the plane, just watch a cpl of movies and arrive into Uk in the evening

For the LHR-JFK sector, I would take the AA105 11:55 service . Not too early a start and arrives into New York for around 3pm. 2nd option would be the 16:45 service

Dave