I retyped their form into Word, used their main headings but then sub-categorised everything in a more logical way. I also made sure every paragraph was numbered and that I cross-referenced important points and highlighted them all.
My final document was about 32 pages long, plus 12 separate appendices, some of which had sub-categories as well.
I then created an easy to follow contents page to make it easy for them to navigate the document and find what they wanted quickly.
Much of this was on the advice of the head of our local inclusion team, who said the most common reason given for children not to get statements in our area is lack of evidence, when often the evidence is there, but they couldn't find it quickly or easily enough.
I made the assumption that I couldn't rely on them getting all the evidence I wanted them to see from 'others' so I included all the reports we had from people like EPs, OT, Paeds etc plus copies of his IEPs, samples of classwork and homework and handwriting etc.
Don't worry about whether or not the evidence you include may be repeating what others send in, that will just serve to reinforce the needs and make sure they can't possibly miss something important.
As Star said, definitely get hold of a copy of the SENCOP and choose some useful phrases to include. I was advised to spell out what issues present ds with 'barriers to learning' or 'prevent him from accessing the curriculum'.
Iirc, SOS!SEN and ACE Ed have some advice on their sites about the process. So it may be worth having a look at their websites.
Mine was a weighty tome, but it did the trick and they have included the main body in the final statement, but without the appendices - which is fair enough, as you'd probably need a crane to carry the statement about if they'd put all that in as well!
You may have noticed that I'm not exactly concise in my writing style,
and as my ds was 9 years old when we applied, we had a lot more physical evidence in terms of classwork etc. So don't worry if your form doesn't end up anywhere near as long as mine. As long as you include everything you have and have clearly indicated where you feel your dd needs support over and above that which schools would ordinarily be able to provide and made sure it's all easily to read and locate the salient points that's all you need to do.
Good luck. 