It’s horses for courses and you don’t give much away about your personal circumstances, but unless you live significantly closer to a Jet2 base than LHR, I don’t think it would be wise to give up (I assume, as you’re still there) a safe place on the BA seniority list to join an airline completely exposed at the lower end of the U.K. outbound leisure market going into a cost of living squeeze, flying an old, thirsty fleet of aircraft around during a period of fuel price volatility.
As mentioned above, there are very few unicorn jobs around and those that have them don’t give them up. I’d ride it out if I were you, at least for another year or so. But as I said, horses for courses.