The biggest problem NCL has is the competition with MAN and EDI. There's no benefits whatsover to NCL or the NE of England of an expanded MAN. An expanded LHR however, is a different kettle of fish as it would allow for connections to more destinations in which the market would be oo small to serve direct from NCL.
I can see the point that the MAN supporters are bringing up, but for a large majority of the country, expansion at LHR can only be a good thing