As for ''UK Regional'' Long Haul package holidayswhich is the subject of this post then Jet2 would have to think carefully -
They could do well at BRS BHX BFS and NCL in the wake of TUI reducing their own programmes, but it's always Seasonal (winter usually), and you're always faced with expensive operational costs with Crewing, Positioning flights, possible split loads, and fuel tech stops needed enroute to destination, and so on.
I thought most of TUI's regional long haul was during the summer?