I went to Mexico on the second Dreamliner flight direct to Cancun from Newcastle this year and paid more or less the same as from Gatwick or Manchester. Looked at all options and NCL worked out the same! It would have been a lot more to go from Manchester/Gatwick if you added in overnight hotel, car parking and petrol.
The flights were almost full both ways. Only one or two seats empty. The demand is there for flights, so I hope they add more long haul.
Out of interest, anyone know why the recently announced flights to Jamaica are NOT on the Dreamliner? Seems strange to say that all long haul flying will be on the Dreamliner, yet these flights are definitely not.