Which companies are hiring DECs that might appeal to those at BA? EZY aren’t, FR isn’t an option for many, Jet2, Flybe might be at regional bases, but the appeal is limited. The UK airline industry has a. extensively consolidated and b. has players that don’t offer career portability. VS, TUI, DHL are the major players I would suggest, and you will only start at the bottom.
Should you wish to continue as a captain, the DEC options are generally restricted to some LCC European bases, or China. Even the ME3 are slow at the moment, particularly wrt DECs.
That's the unfortunate truth, hence choose your career path wisely.
I really don't understand those posters who think seniority is unfair. You just cannot expect to jump the queue at any major after a couple of years in the low cost business (or elsewhere). Whadya think those FO's who've been in the company for 15+ years would think? Fair?