@PatriciaHolm Thanks for your answer. The recommended OT is currently 2x per half term, plus some sessions in school. The OT has an existing relationship with appeal school due to prior engaging with kids there, whereas this is not the case for allocated school. She has confirmed this and this is part of the additional evidence I submitted.
However, we are only at the beginning of possible further assessments for my son. ASD has been raised by both the OT and his current school, so we don't know how his OT needs might develop.
Our other main argument is that the school offers a modern language he has got an association with, and that modern language is usually under- rather than oversubscribed.
The school has made a fairly robust defence about being oversubscribed. However, they would have done this in previous years, too, and yet approx. 20% of all appeals at this school are won!
As for arriving during first / just before 2nd period, we can say that at appeal school, he will definitely be able to join for start of the 2nd period (with room for a breather if the school don't want him to join for end of 1st period), whereas at allocated school, anything going wrong on the journey would prevent that, and he'd likely also be more tired from the trip.
We didn't mention at all in any documents that he doesn't know anyone at allocated school whereas at appeal school he has got a big friend group. Should we make a thing of this? We though this might weaken rather than strengthen our argument.