Leeds is Jet2's home and I think the new aircraft should be kept here not only for Jet2's personal fame but for the thrill of Leeds having some new planes to the airport.
Jet2 will base their aircraft where they think they can make the most money and be most effective. If Jet2 think their 737-800s will perform better at Manchester, Glasgow or anywhere else they will base the aircraft there.
Jet2 and all other airlines do not base aircraft at an airport just to please the local spotters.
Anyway, putting that point aside, have Jet2 even confirmed they have these new aircraft yet, never mind said where they will be based?