Sparkletastic - goodness no! I am just a parent with a child with SN. She has a brain malformation which is quite subtle, but affects her in almost every respect in some way, including behaviour.
I know what I know from many, many hours trawling the archives of the SN board, and reading all the experiences of the other parents on here.
WRT pushiness - You need to take control of the process. If the 'school' apply for the statement, they have no right of appeal. If you wait until your DD is in reception year, then she will spend most of that year with very little support whilst the application is processed, and the LEA may well say that she has to be shown to make no process on School Action, then School Action Plus, which are the 'in-house' special needs categories under management of the individual school.
You don't need to be agressive, but just very very aware of what is the right procedure, what you want, what your daughter needs. You need to be unwavering in your certainty that without substantial additional support, your daughter's education and welfare will be failed.
Clinical evidence is of course crucial, because that is the 'teeth' of your arguments. What parent wouldn't want their child to be prioritised given the chance? Having a hearing loss on its own is not reason for help. If your DD is an expert observer of body language and lip reads, she may not be at any disadvantage, for example. Having a brain malformation on its own, in my DD's case, would not be enough to give extra help. It is the effect that has on DD that will get her the help.
You may need to be even more assertive if your DD is quite passive and well behaved, because if she doesn't cause trouble to the teachers, there is a tendency to think the child is OK. You need to push for her to receive an education that will let her meet her abilities, not just 'exist' in a classroom.
I would highly recommend spending a few hours looking at past posts around statemtenting. And send that letter!