BA tend to let new entrants know about their courses about 2 to 2 1/2 months before.. I believe you ve got till may until your offer expires...if i were you i d wait until next year till about feb then i d get worried and maybe consider other options as its unlikely they would call you in april fora course two weeks later...with t5 coming soon,things are getting very busy for the company and i am sure they will have completed recruitment well before april....