@overworkedrobot Thank you so much for your detailed questions. Some are hard to read because they show how naïve I've been for the past year but I need and want to hear them so I can pull the plans on track.
The EP report should be in the EHCP in section K, is it not? Yes, it's part of the appendices, but senco says she's not received it. 
If the transition provision was in the EHCP and hadn't happened you could have insisted on it by threatening Judicial Review.
The provision should be very detailed, specific and quantified. Nothing should be left for the school to decide. Who, what, when, where, why, how... The provision was definitely not quantified but they haven't even met the unquantified provisions which could have only taken place before teaching started. He hasn't been introduced to teachers, doesn't know who his key worker is, there's no quiet space to go to during breaks other than form classroom and he's not been allowed to stay in on at least one occasion.
The EP recommendations were quite specific and would have been common sense anyway for a child at risk of school refusal (which his whole EHCP is based on, really). I went to an EP drop-in this week and the psychologist couldn't believe her ears. The only actual adjustment made seems to be that he's in a small class. He seems to be one of the more independent children in it and just been left to get on with it until the meeting a couple of days ago.
My feeling is that the school is simply not ASD informed enough. They hear the bell of the need for adjustments but don't seem to get that these need to be embedded from the beginning and throughout - not just as interventions that can take place at some point after we all settle into the new year.
During the needs assessment did DS have SALT, OT and some sort of mental health assessment (psychiatrist &/or clinical psychologist)? No, he only had an EP assessment and an ADOS. Can I insist on adding these to the plan or would I need to organise these myself?
Be careful with the advocate, not all are good and some can make matters worse. If you are short of funds prioritise independent reports over an advocate. I get what you're saying and as I'm learning more I guess I'll be able to. I got the advocate because I needed to keep the appeal process going while I was stuck in anxious paralysis and our local SENDIASS was not great at helping with this. But I can see that after these first EHCPs are settled (my other DC is also in the middle of this process), my money is better spent on reports etc.
I'm not eligible for legal aid and struggle to get the help from organisations that I need because of my own communication needs. I seem to come across as this argumentative but on-the-ball person, while actually I'm the complete opposite: too easily swayed by the other side's concerns and completely hopeless at managing more than one process/task at a time. My written submissions are clear and detailed, but it takes me months of anxiety to start writing them. Masking at its finest, I suppose.
The TAC is probably too long away. If DS is still unable to attend by then I would be worried he will struggle to ever integrate in to MS secondary. I agree. If he still refuses to go in on Monday, I'll call for an emergency meeting with the HOY there, to formulate a plan of what to do while he's struggling and until the appeal.
However, if he is absent for 15 days the LA must provide education for him outside of school. Is that 15 days total or consecutive?