I would suggest that any experienced pilot applying for a BA job in the future not bother until BA have signed and delivered to you a note that promises your employment ahead of any cadet. Otherwise you're wasting your time, effort and money on what is essentially a recruitment methodology that is as worse as RYRs (remember the outrage when they charged €250? well attending BA assessment days can cost some people £2,000 a pop if they're travelling from the Sandpit or Far East over 2 or 3 separate days).