Hi
You can tell when your interview might be by the number, looking at last years bulletins. Generally if it is a really really high number, your chances are less, but that depends on what region you are from.
If you send off your forms quickest you will get processed before the slower ones
You do not have to send money at that stage.
Some people wait months before sending off their forms, but I would not wait - it is still a lottery at that point even though you have a number.
The police and education checks are done after the initial forms are sent back.
Good luck!
Q
Thanks for your answer that clears things up. Much appreciated. Good luck!