This is a question full of hypotheticals. I know that absolutely nothing is predictable, but I am running through possible situations based on what's happening now. If that makes sense!
We may be moving away from our lovely primary school to spend a year overseas. We would then return to our same address & hope that we got a space there again... At the moment there are 5 people on the waiting list (2 in catchment) in my daughter's year. I know we would go to the top of the list because we live so close to the school.
if we were to be moving back now, there are two places in my daughter's year across the whole of the borough - one 2.5 miles away & one 4.6 miles away.
The council suggested that, because we would be looking for a Y3 place, we would be in a good position to win an appeal for in-year admission at our local school - I suppose that would force the class number up to 31 - because we could show there were personal & social reasons that she would benefit being there.
Does that sound possible to you? We will be going away anyway, but I want to have fully thought through the consequences of the move for our DD...
It is possible but I wouldn't bank on it. If the allocated school is only a couple of miles away the appeal panel may well decide that your argument is not strong enough. However, in your favour is the fact that this will be a Y3 appeal so infant class size limits don't apply. And if the council said that in writing I would put that in evidence to the appeal panel and suggest that they led you to believe you would get a place one way or another.