Thanks for everybody's advice and comments. I think it is likely that we will go for the WT+ flights. I understand the desire to take the day flight back from NYC and on the day that we are looking to fly back from NYC it is currently on a 747 however I would rather avoid the day flight simply because one misses a whole day in NYC that way or has to take an extra day off work. By departing Friday afternoon from LGW I get a half day at work on Friday and then an overnight flight back from NYC on Tuesday means I can get a full day at work on the Wednesday, or at least a half day if I need to recover at home for a bit after the flight.

I have taken the LGW flight to JFK before and agree with c-w-s that it is perfect timing to land, clear immigration and then head to the hotel and sleep before a full day the next day.

There are comments about the LGW service being cancelled, however if it does get cancelled then I am sure BA would just put me onto an LHR service instead, preferably similarly timed, so is that really something to be worried about?