I sent in a 5 page document.
It started with a 'Background' to the statement request - Pregnancy/birth concerns; early development & milestones (delayed); concerns raised and action taken (none ); Preschool identifying SN; Hospital attendance & confirmation of epilepsy, GDD and brain malformation; Support measures given at preschool at EYA+.
I then moved on to 'Present difficulties', broken down into Gross motor; fine motor; speech/language; social; attention/concentration; behaviour; sensory features; obsessions; sleep; medical features.
The next part dealt with 'considerations for assessment' in which I summarised the complex nature of DD1's special needs, that a report from her consultant said that children with her condition usually require a statement, included a phrase from the SEN COP, which said that "it is unlikely that any school can meet DD1's needs without employing extensive additional support, for which a statement will be needed." I also pointed out that little progress had been made in her preschool career to date, and that the gap had widened between her and her peers. I also asserted that there would be a H&S risk to both DD1 and other pupils if they left her without support.
The final page listed each of the reports that I was sending to support the request, giving name of professional, position, and date. I sent in every report I had available (18 in total) at this stage.
I hope that helps. My LEAs pack requested this information, but gave a tiny form to give it, so I typed my own. I would be more than willing to let you see it if it would benefit you. I am sure others will have done it differently, though