Don, it is not automatic that you'll go to flight screening. If you are successful through assessment day and get recommended then your dossier gets sent to PSA with everyone else who's recommended around the country. PSA give your dossier a score and put it on a pile. When it comes time to select the 7 or so lucky ones for the next FSP they go through the pile and select those that they consider to be most competitive.
My dossier has been down at Tamworth for about 8 months before I got the call to attend. Your dossier will stay for a maximum of 12 months, if you don't receive a call you're deemed uncompetitive and will have to reapply and go through assessment day again. There are some people who have waited out the 12 months before getting a call, there are others that don't have to wait very long.
Coran