Hi scratchingthesky,
I believe most airlines have a three month notice period but I am confident that the next bmi course will be run with far less than three months notice.
Its then up to you if your going to accept the job and give your present employer less than the required notice.
If you feel its a significant step up, then you have to look after yourself and your career.
Tough decision I know, I am debating it with myself at the moment
Fingers crossed for some news soon
Best of luck
