Just booked a return flight to JFK in August at £274.10 from Manchester.
Been searching for ages and all other sites and carriers are at £570+.
Expedia seems to be having some special deals since BA site is at £600 for the same flight.
Not sure whether it applies to all airports, or the dates it covers - just seems that you have to avoid flying on a Sunday. Just checked £249 for the same dates as mine from Heathrow
Oh and there is 1% thru Quidco too.