Verbal dyspraxia and dont want my child to go to a mainstream school.. any advice??

[kiimmia]

I`m really not sure what to do and sorry if I go on a bit... My son is 3 yrs 9 months and due to start school in September. He hasn't officially been diagnosed with verbal dyspraxia as his speech therapist says he is too young to make any diagnosis. He has seen so many specialists and had tests and assessments and they have all said that is what he has but they cant diagnose it as it has to be someone from our area in our speech and language unit. The last person I saw at oxford cleft centre (they wanted to rule this out) said he has quite severe verbal dyspraxia. He cant say his name and can make some sounds such as oo, ee, ah but there are sounds he cannot make and dada comes out as baba and if he tries to form a sentence it is mostly ah ah oo ah (for example) its babble really although we have come to understand they very few words he can say, we don't understand everything and he gets very frustrated.. other people have trouble communicating with him.
He is starting to sign and we have signed up with a signalong tutor who will come to our house and teach us. His playschool are very helpful and are also helping him sign.
We are hoping he can go to a school with a speech and language unit attached to it and our health visitor and pre school support us on this and feel this would be best for him and in a mainstream school he would not be able to communicate with any other children. His speech therapist is less helpful and seems to think he should go to mainstream as in her words "reception is only really play based anyway so it doesn't really matter about the speech side of things".
He has still only had one session of speech therapy this was 4 months ago.. prior to that he had someone come and give him some tasks to work on 6 months earlier. This woman has met him once only and it seems as his mother my point of view means nothing.

Just wondering if anyone can give me any advice on getting him into a special school that can help him more or if anyone has had a child with severe language disorder (this is what she calls it) although I would say its slightly more than a disorder when he cant talk.
She said he will get a TA with him for the mornings and maybe 2 afternoons.. but what is he meant to do for the rest of the time?
Any advice is greatly appreciated.