Skyman -
My logic is related to the debate in question, not the London area.
I don't think it is too extreme to suggest that SLF from Leeds/York, both fairly affluent centres, would choose DTV over MAN, but not NCL over MAN.
They won't do that without clever, targeted and consistent
PR/advertising.
If DTV wants to attract passengers, it has to play to its strengths. At present its strengths are accessibility, uncongested, swift terminal access.
Furthermore, if NCL attracted a NYC service, it would be competing with the Continental flights from EDI. That's less of an issue at DTV.