I am not able to comment on much of what has been said, as my children are now adults, the system seems to have changed since my time. But having dealt with social services and education, then later worked for social services for a short period of time, I do know something of how the system works.
There are procedures and protocol that these agencies are bound by law to follow, guidelines state that if a is diagnosed with xyz, or deemed to be in need of a service because of abc, once the assessments and paperwork has been completed the agencies are legally bound to provide funding to cover these situations.
In practice it doesn't work like this at all, due to funding issues. The agencies although obliged to provide whatever is deemed necessary will do all they can to avoid responsibility to find the funding.
I have had personal experience of this situation, it took me years to get tripartite (I think that was the term used) funding to access a therapeutic community placement for my son, the home situation was dreadful and he was in desperate need. The whole family suffered hugely because of my sons problems.
Like you, I started to process expecting procedure to be followed and then to be able to access the help needed, but each time I won a fight with the departments, I expected something to be provided, it wasn't. This went on for 7 and a half years during most of which my son did not regularly attend school.
By the time I got a solicitor involved, it was too late, we got the funding, to discover that at 13 and a half, my son was not eligible to attend a therapeutic community, my next step was to have him put in a secure unit on welfare grounds, which in the long term did help, it also almost destroyed our relationship. Then, when I felt he had learnt a lesson, he was released, social services used the funding I had fought so hard for, (which in my mind was for intensive medical therapy,) to fund a placement for him in a specialist childrens home to contain his behaviour!
I know we had different problems, totally different situation for us, but if I could go back and do it again, I would have involved my mp. once you do this, all of the agencies jump! they are then answerable to someone in authority, they are forced to follow the letter of the law, to either provide the recommended treatment or have a really valid explanation as to why they are not following legal procedure.
It would be very sad if you have the experiences we had, which was a constant fight, just when I thought I had won, (eg a statement of education should provide extra help, it didn't) a spanner would be thrown in the works. this went on for many years. My son is 25 now, although he is much more able to cope than specialists predicted, he doesn't have a life, he still has problems with perception, personal responsibility etc. It breaks my heart and I would hate for any parent to trust that the agencies will provide what is needed, only to discover when damage is irreversible (eg lack of education) that there was more they could have done.
If I have misread anything you posted and this isn't relevant, please remember I have my own issues of comprehension etc,