Hi Piffle
My first advice is if you think that your child will be able to get a statement, then do it and get the ball rolling as soon as you can, in my case it took a year to get a statement for DS2 and he was already in school. It would be much easier to start a school with the help already in place.
Also it can mean that you have more options as to which school they can go to. Do bear in mind though that it does not automatically get you in to any school you may wish for, it depends where you live and how many other statemented children there are in the school.
With regards to missing reception, I think if you are sure that you want her to go to a particular school, then it would be a shame to miss reception, because this is the year that is the most fun and the children have more freedom.
Year one can be a tricky year for some children, because the pace does change and they do not get anything like as much free time. They have to sit and listen and do a lot more work.
But if you are unsure where you want her to go and you want more time to see how she gets on, then leave her where she is, if she is happy and you are happy then there is no need to rush into a change.
I wouldn't worry about the not writing bit though, whatever you decide.