As I had a lot of PM concerning selection, here are some tips I can forward.
Please note that it is concerning S/O selections process and was held in october 2005. Some things might have changed since then.
Location : Heathrow BA training center lasted 1 day
Sim : Bac 1-11 basic raw data flying "CX style"
Interview : 20-30 min basic HR interview (motivations, why do you want to quit your current job etc...)
45-60 min technical interview (all ATPL topics can be covered)
Good book to prepare "ACE the technical pilot interview" by Dan Bristow. A few mistakes on some topics in this book but still great. By the way there is a forum concerning this item.
No written tests at all
Once again this was almost a year ago, so do not take these infos as the bible !
Good luck to all of you
Blue skies