Desk-pilot,
regardless of who you fly for it will not be as a cadet because you are too old so your salary will be a DEP one. If you join BA you will have plenty of CEPs above you in the seniority list, it could take you a while to get a command and bare in mind you will never get really high up the seniority list because of all the aformentioned CEPs who will retire after you do.
Anyway, thats mtpw,
cheers