To explore this topic fully it really deserves a thread of it's own, to do it here will only dilute the benefit of this thread for those interested in joining BA.
In brief, the seniority system sounds archaic when you first hear about it but I have yet to hear anyone come up with an alternative that is (even nearly) as good. It has it's downsides but it is completely fair, transparent and safe. It was discussed here [
http://www.pprune.org/questions/4156...bad-thing.html ] a while ago, the flaws of the seniority system are acknowledged but the general consensus is that it is the best system.
The important thing is that you know BA has a seniority list and how that will affect you when you join.
All 737 training up to (but not including) line training is done at LHR. Accommodation isn't provided but there are some allowances that can be claimed to cover your extra milage (only if your home address is closer to LGW).