If you're just looking for a cheap flight (ie. FF points for this leg aren't an issue) then Zoom Airlines offer pretty good fares across the Atlantic.
Flights from JFK to LGW are around US$350 (tax incl.) one-way for economy (which includes a 31" seat pitch, dedicated check-in and 20kg baggage, with 1 meal, 1 snack and free soft drinks throughout the flight)
Price goes up to US$530 (tax incl.) for premium economy (36" seat pitch and 30kg baggage, seat selection, free drinks incl. alcohol, choice of meal and 1 snack, plus headsets)
Just an option should you just want to get to London. I think they also fly to Paris from Canada should you want to start your home leg from there.
Website is http://www.flyzoom.com