A few hints:
1. Try and "tap up" a recent short haul recruit for the realities of working at BA.
2. T&Cs are very fluid, take off the rose tinted specs. ( e.g. rostering agreement in a major state of flux/meltdown).
3. There is indeed some discontent at the moment, BALPA are doing their best but....
3. You will be very much working for the UK arm of IAG (perhaps that's why the language in the advertisement may be a bit adrift
).....IAG now call the shots.
4. Look at Vueling's T&Cs......( if you're asking "why?", have another read of hint number 3)
Good luck