I thought the LA expected us to have an idea of what support DS1 needs and what help we require for him.
No, that would be prejudging the outcome of the assessment...
however...
If the LA do decide to undertake a full statutory assessment they will ask you to provide Parental Advice. In that you can state whatever you think would assist him. The LA are supposed to consider your views as parents.
The Parental Advice then becomes one of the Appendices to the actual Statement.
We are expected to identify his needs and provide evidence for them, but the LA identify the difficulties and the correct support, is that correct?
Partially. What you are saying to the LA when requesting an assessment is that 'my child has learning diffuculties' and some evidence to support that. The extent of those learning difficulties are only revealed during the statutory assessment process. Once these difficulties are identified and their impact assessed they are described in Part 2 of the Statement. Then, for every difficulty described in Part 2, the LA will detail what support is required to overcome that difficulty and list all the support in Part 3.
Do they choose who will make that assessment?
In the statutory assessment the LA contacts everyone who is in contact with the child and asks them to provide their opinion in a written report. This will be school, you as parents (Parental Advice), the Educational Psychologist, the Community Paed, any other Paeds or HCPs he is seeing, Social Services (don't let that worry as they are only asked if they are currently in contact with your family) and anyone else at all that you tell the LA you want them to contact for advice. You can also provide private Ed Pysch reports etc but this is definitely not needed for a statutory assessment.