Its highly unlikely to be Jet 2 leasing a 737 300 out in peak summer months , they would have already have had that aircraft fully committed for this summer , bearing in mind as well Fly lolo up until very recently were looking at an Austrian E 190 to use
Jet 2 have also said they willl not be opening up any new UK bases in 2020 , and i think everyone is agreed the B 738 is not suitable for SOU operations anyway as their B 733 will be gone by next summer