Very surprised that LBA was chosen I was confident that FR were bound for MAN on this one!!!
I think that Jet2 has a very well established name and brand in the LBA Area. And yes it will be cut throat for a while. It may be very like BFS where Easyjet (who is v well establised) has Aer Lingus (who would be as well know in BFS area as FR would be in LBA area? Probable debate on this!!). Aer Lingus took Easyjet on in key markets eg AMS, CDG, BCN, GVA, FAO etc. many of which are now withdrawn or being withdrawn.
The difference in LBA is that FR will not axe routes in the face of competition from Jet2. Ryanair will be in for the long run.
Good luck to Ryanair. I still think that MAN is the ultimate desired destination and as has been mentioned on the forum MAN will be under pressure for LBA and LPL for low cost traffic, when MAN decide that they want this back and put the deal on the table Ryanair will go for it.