We did Gatwick - Orlando last Easter with BA (777) family of 4 £1,500. Excellent on-time (push was 2 mins early at LGW) WORKING seat-back entertainment for the young'uns, food OK, friendly service, comfort of knowing there's a backup a/c at LGW.
I know it was in Economy and no seat/upgrade available as it was packed, but felt confident that the airline would get us there and back when they said they would (as indeed they did) The best price we found was Icelandair via Reykjavik and LaGuardia which I would have preferred but not with a family in tow! and it would have taken twice as long.
Good luck to anyone trying something new, but remember what happened to Freddie Laker when he tried a premium service UK-Florida, using an a/c type he was familiar with...
Cheers,
The Odd One