I don't know where you are flying to in the states but Norse Airlines have super cheap tickets. They are no frills but I got tickets for myself and my 3 children for £1400 one way. I chose the middle price option as it included a carry on, a checked bag, underseat bag, and a meal. We then added more checked baggage for a total of 10 checked bags and priortiy boarding. That was from Gatwick to New City. Our final destination was Pennsylvania. If you only have one checked bag, you can book a flight from NY to your destination but as we had 10 checked bags, that would have been way too expensive. So I bought 4 Amtrak tickets and with all our baggage was about $200USD. We did have to stay in a hotel $311USD but we did choose a 4* only becuase it was right across the street from the train station. I forgot to add, I paid for a private driver mini bus service to our hotel. That was about $240USD. All in, we paid about £2100 and it was an adventure! Our train journey was 8 hours but we loved it! If I were to divide that up between 4 people, that is £600 each. We paid for all this from selling things that we couldn't bring with us so not a penny came out of our bank account. We did stay the night at The Bloc Hotel right in the airport and got the rooms that had the runway views. That was out of our account but a great last night treat in the UK. It also meant, we were already at the airport, you only had to take the lift down to check your bags in and then security. The Bloc Hotel gives all passengers fast track security passes as well.
My husband is flying over for a visit in Dec. and his round trip ticket with BA is about £1000. I'm sure there are some good deals out there but thought I would share what we did to save. Norse doesn't have the best reputation but we were 100% happy with the service but it just depends on where you are flying to.