OnlyOneRudder,
As far as I am aware the industry standard notice period is 3 months. Mine is 3 months with my current employer.
As I said before, there were lots of dates available in November to choose from so those that have not heard, don't panic too much. It may just be taking time to process the high volume of applications. I have no idea the order they do it in but one would assume that next week we should see more invites being sent out.