We were still waiting for the school to outline exactly how the timetable will look and when they do that will be added to the final EHCP. 
This sounds as though the LA is basically making your child's EHCP fit the school they want to send him to. That's not how it should be. The school has to meet your child's needs - all of the needs identified in the assessment reports gathered during the EHC Needs assessment, (including the CAMHS information.)
With regard to the EHCP:
If the EHC Needs assessment has been done properly, the LA should seek advice from all of the following people:
- the child’s parent or the young person;
- educational advice (usually from the head teacher or principal);
3.medical advice and information from a health care professional;
4.psychological advice and information from an educational
psychologist;
5.advice and information in relation to social care;
- advice and information from any other person the local authority
thinks appropriate;
7.where the child or young person is in or beyond year 9, advice and
information in relation to provision to assist the child or young
person in preparation for adulthood and independent living; and
8.advice and information from any person the child’s parent or
young person reasonably requests that the local authority seek
advice from.
(If your child has autism I would ask for advice from SLT, OT
and an autism specialist teacher.)
This list is set out in Regulation 6(1) of the Special Educational Needs and Disability Regulations 2014 (the “SEN Regs”):
All the professional reports should identify all of the needs the child has (which will go in Section B of the plan) and there should be provision to meet each one of these needs (which will go in Section F of the plan).
The provision should be very specific and say who should be doing what, how long for and when.
Go through all of the professional reports with 2 highlighters. Highlight all of your son's needs (ie all his difficulties eg poor organisational skills, difficulty with time keeping, slow processing) in one colour and then all the provision to meet the needs in another colour.
For example you might have a Speech and Language Therapy report which says "X has great difficulties with social communication." This would go into Section B of the EHCP. The SLT might go on to say "X needs a social skills programme devised by a qualified Speech and Language Therapist and delivered for one hour each week." This would go into Section F of the Plan.
When you have done this for each one of the reports, go through the draft plan and make sure all the needs you have highlighted in the reports are in Section B and make a record of any that have been omitted.
Then make sure all the provision you have highlighted in the reports are in Section F and again make a record of any that have been omitted.
Give the LA a copy of your records of missing information and tell them that everything that has been missed out needs be included in the final EHCP.
If any reports are vague or woolly and use phrases like "requires access to", "would benefit from," "regular" "high level of" tell the LA they are not acceptable and they need to go back to whoever wrote the reports and make them more specific.
With regard to the school:
If the EP has written that your child needs small group learning in every session then the school named in Section I of the EHCP has to be able to provide this. As it is highly unlikely that any mainstream secondary school could provide this, it seems as though the EP was indicating a special school as they typically have small classes.
You mention the LA preferred school is talking about a part time timetable. This is not acceptable. Your child is entitled to full time education just like any other child.
Ultimately if you are not happy with the final EHCP, you can appeal, but I would go straight to appeal and not bother with mediation, as time is running out to get things sorted out for September.
Is the school you feel will suit your child best fully independent or is it a Section 41 school?
If you want to talk to somebody about all this you can book an appointment with the IPSEA advice line. You might have to keep checking for a vacant slot though, as they are put on at different times of the day.
www.ipsea.org.uk/advice-line