NorthSouth
There is no hard evidence to disprove that some of the extra pax at NCL were gained from MME either.
I agree that residents of Middlesborough, Darlington etc are unlikely to fly from NCL instead of MME to AMS, however is it possible that people who live approx equal distance from both airports were swayed to NCL over MME because of the passenger charge at MME?
In addition the uncertainty over the future at MME could also be a factor that has affected bookings. Timings, road/rail access? I really dont know the answer.