Lincoln to EMA is easy enough, both by road and train, 1hr 15 by road and about the same by train. Leeds is far more like 1hr 45 on a good day!
Regarding the catchment area for the routes its is very heavily dependent on Lincolnshire and the farming areas around the Wash, but does attract people from as far north as Darlington.
A better split would be for Humberside and Norwich to share the routes, but I doubt that ll happen