Firstly congrats on getting a new job, I hope that the grass is greener on the other side, you have certainly made your feelings known re Jet2.
I think that it depends on how you leave the company, I know of only one, but maybe there's more, that haven't been given a reference. As far as I know the individual concerned left and refused to pay his bond. Now I know that this £5k bond whilst already type rated when joining seems to be a bit of a sod, he signed it of his own free will. Now if you go about things correctly and maturely, work your notice period and come to some arrangement which is mutually agreeable re any bond that you might have then I can't see a problem.
Good luk with the new job.
Jonathan