During the foster care process, one thing the agencies are looking at is if you are looking for a back door to adoption (and many are) and they *really* bawk at that. The purpose of foster care is a place to house children in a safe nurturing environment until mum and dad get their act together. CP's goal is family reunification.
If you do become a carer it's unlikely you will get a child on a PC order. Usually they start out on Custody or Guardianship Orders and they are placed with you. Then after several years of the parents not dealing with issues they then look at permanent care. They will then give that child to the family they were already placed with all those years.
So getting a child on PC can take years, and you can't be guaranteed to get a child that will get to that point.