Glipglop, good luck.
despite the anger at BALPA, BA is still a great company to work for, it has its's challenges but so do all companies.
there is plenty of advice out there about the interview. It is an evidence based interview - give me an example of when xxxxx. Be aware of BA as a company and its position within IAG. How it is doing financially and what challenges it faces. and all the normal stuff too,