Does that mean that the school is definitely oversubscribed at this time?
No, transfer appeals will still be arranged regardless of the current position. Once the second round of Admissions takes place those who receive a place will withdraw their appeals, and that process continues until either the appeals take place or the school can admit all those on the waiting list, whichever comes first.
I have heard of quite a few occasions when parents have received calls from Admissions the day before the appeal telling them that a place has turned up. I believe that there have even been cases when parents have arrived for either the first or second stage of an appeal, only to be greeted by someone from Admissions telling them that a place has come up and their appeal will therefore be unnecessary.
Does anyone know what happens to the school's waiting list if the IAP go to Stage 2 someone's appeal isn't upheld? That decision is apparently final so what if a place later comes up at the preferred school? Am I disadvantaging myself by appealing?
You are not disadvantaging yourself by appealing. The IAP's role is to decide whether the school can admit additional pupils over the PAN of 150. Even if your case against over-subscription is not successful your child can remain on the waiting list and, if places within
the PAN come up, they will be allocated to those on the waiting list.