I agree that everyone should try to be positive and patient.
Remember that the recruitment has only just begun and will likely continue for some time.
Also however remember that like Ryanair, Jet2 is very much a low cost airline taking any and all cost saving measures in these difficult times, including external recruitment in favour of internal promotions and transfers.
I'm sure Jet2 is not restricting itself to UK citizens, although I expect those being selected for interview at this stage are likely already situated where vacancies are forseen for next summer.
It is difficult to know what sort of contracts Jet2 has in mind. Jet2 may well offer a choice of temporary or permanent part time.
It is also likely that all successful candidates will be placed in a hold pool and may be offered a job only when Jet2's precise requirements are known, probably in the spring.
I suggest attending the interview armed with many questions, and then let us all know the answers.