Jet2 is a 'no frills' airline which is fine for short distances but I'd prefer not to fly further than 3-4 hours with them because they're not the most efficient or comfortable of airlines.
My family paid for extra legroom in row 12D & E and 14E & F as I suffer from mild claustrophobia, but 14E had no extra space. The seats we're located halfway down the plane by the emergency exit doors (the area can get very cold in flight) and not only was it a parking place for the drinks trollies but people also stood here to exercise themselves and their toddlers, we were constantly moving our feet out of the way instead of being able to stretch out. The tray tables had to be fitted into the airm rest and were totally inadequate, you have to balance everything precariously on a flimsy surface 1/2 the width of the seat. Basically, unless you have to, don't bother with extra legroom seats.
Another gripe is that the free allocated seating is so random, with couples being seated rows apart on opposite sides of the plane that you're almost forced into reserving seats at extra cost if you want to speak to your travelling companion!
We were pleased, however, with the food which we ordered online beforehand at a discounted rate. It was good quality and choice plus much cheaper than the available snacks/ meals on the flight back.