Perhaps your interview has been postponed due to redeployment of ground staff from the now-closed (or closing) regional bases to cabin crew based at LHR?
Either way, I feel very sorry for those still in the application process or without dates for a course.
Unfortunately, this is the bad side of the company...they can be VERY disorganized; you will come to notice this after a few months at work (which I hope will be the case for all of you).
Our crew numbers NEVER seem to be 'right'.....one month we are apparently short of crew, the next we have too many.
For those of you joining the airline industry for the first time, remember this: CHANGE IS ALWAYS IN THE AIR!
Good luck to all of you.