Tigertanaka,
To Jet2 's credit their model is significantly differentiated in that they drive Jet2 Holidays, which is a strong one stop shop for family package type holidays.
FR have traditionally picked its battles worth weaker rivals, they've put enormous competition easyJet's way, so much so easyJet no longer have bases in Rome or Madrid, clearly it is more than Ryanair who had added to easyJet's woes in those locations. Nonetheless, entry on STN GLA and EDI and more recently BFS, all make file quite a statement.
So I'd say the challenge especially currently by FR to easyJet is enormous.