Sorry I do not why LTN needs a Jet2 operation as it could only take place at the expense of Monarch and EasyJet. Together and with a contribution from Ryanair and Thomson they cover most of the destinations than Jet2 does from Stansted. As it is they may be having an impact on LTNs ability to serve this market.
To me it seems that Jet2 are rather flooding the market at the moment and somebody is going to get hurt. As the B-word feeds slower growth and more inflation into the UK economy the market is likely to become harder over the next few years and that will impact the "UK originating bottom end" most". Jet2 is IMHO most vulnerable in this respect. Just like Court Line in 1973/4.