don't be scared of the tribunal! I was, and wasted so much time because of it. It's there to protect your child's right to a decent education, the ability to appeal is a good, GOOD thing! I know it sounds daunting and as if you are up against a mighty institution, but the process is designed to enable parents with no legal training whatsoever to register and defend an appeal themselves. It's good to get advice in particular if you are in a London borough as the LEAs there do tend to defend, but don't be intimidated - easier said than done I know.
In 90% of appeals where the reason for appeal is LEA's refusal to asses the LEA conceded without a hearing. IPSEA can help you with the case statement. Remember you just need to get them to assess her, and give reasons why an assessment is necessary ie. a) she needs a statement and the only way of getting one is through a stat assessment, b) her special educational needs cannot be determined without a statutory assessment.
Finally, and this is what did swing it for us so quickly that I barely managed to register the appeal:
Request from the Case Manager in the LEA, in writing (e-mail him/her) the Local Authority's written criteria for statutory assessment. They all have one. Say something like 'I would like this within the next five working days'. They can't refuse to send it to you. Then go through it, and I bet you a million pounds there's something that applies to your daughter. I found, for example, that Southwark's own criteria for statutory assessment stated in black and white 'a diagnosis for ASD'. I then emailed to the case manager and copied the head of SEN something like 'In your own criteria for statutory assessment it says... diagnosis for ASD... By refusing to assess my son you are acting contrary to your own written policies. This constitutes maladministration as defined by the Local Government Ombudsman. Unless the Local Authority initiates a statutory assessment as per its own policy, I will complain to the LGO immediately'. A week later we got a letter saying that they will assess. Go at them, they'll buckle as they'll have plenty of opportunities to get difficult later on (they'll refuse a statement, you'll have to appeal again, the statement they issue will be crap, you'll have to appeal again... it's hell but worth the fight in the end).