We're good OP xxx. I have experienced a lot of anger about this issue too. In the past I actually described my feelings as grief.
This is clearly a case where it would do no harm and it might just do loads of good to defer. A good system would recognise that. You are being forced to do something that you feel may be against his interests and that's not what you want at this stage of his life with you. I feel that it is critical that you do whatever you need to do to nurture your relationship with eachother since it is ultimately from that relationship that he will develop. I apologise for speaking without knowledge of adoption but I learnt enough about special needs to understand that children develop and flourish out of relationships with those they are bonded with.
For know how and facts, get yourself to these forums:
www.facebook.com/groups/121613774658942/
groups.google.com/forum/?fromgroups#!forum/schoolstart
If you want to fight, they will pop up and help you draft letters/know what to say, etc.
Re school and medical people, you have to either build alliances or be such a hard person to beat that the matter gets escalated to someone more confident and capable.
Is building alliances an option? Realistically, at this stage? Is there a nursery attached to school? Can the adoption community advocate on your behalf? I feel the adoption issue is key here.
If the doors really are being slammed, remember that you have options. You can take another year out to be with him and decide in November whether to apply for a year one place or keep fighting. Have you applied for a place for this year yet? You also have a right to start him next spring instead of now (assuming you applied for a place). I would definitely have him in a school nursery from September if he isn't starting school, and definitely one attached to a school.
You can also think about moving to a school where they have mixed year groups - that is common in very small schools and in 45 kids per year schools and can work well for young August-borns. You can think about moving to another LEA or even Scotland. I know that sounds dramatic!
Your comment about needing time to bond with him is resonating with me. I kind of have a gut feeling that you must do what in your heart you feel would be best for this key relationship to flourish.
Back when things were hard, I used to have this regular sense that, by taking a different path (no school but no diagnosis either), DS2and I were alone up a mountain together. Other people kept telling me to come back down the mountain. They insisted that would be better for us. But actually it was just that it would be more convenient for them.
So I would consult with adoption experts and work out what is in his best interests for the next nine months, then simply do that thing. That will change the game (no one took me seriously until after I let the default year application deadline pass ).