As you say Joe Curray, GSM are best to conentrate on long/medium haul flights where EZY and FR currently havn't ventured.
However, I don't think Jet2's 'days are numbered.' LBA is a huge base for the airline and is always going to get bigger. They have pulled alot from MAN but they still have a big presence there along with BFS and NCL - two U2 bases. They also have profitable ops at both BLK and EDI.
Don't count these carriers out. Jet2 is not a stand alone company, it is supported by a major firm that deals with other matters aswell as aviation.