You will find the winglets are already fitted to the one parked up in LTN, the other is in the middle east having a check and getting them fitted.
My understand is that Jet2 have already carried out some of the acceptance work on the B737NG, but some problems have arisen between the leasing company and Transavia on the hand over.
Jet2 are also getting a B737 classic in time for the summer, along with the second NG.