Thanks for all your advice. Whatever the outcome, it was great being able to go into the hearing knowing what was going to happen, and having a well prepared arsenal of facts and positive stuff to say. We're very grateful.
Currently I have no experience of these, but you will find further details here. My sense is that where a complaint to SENDIST is also possible, the latter is preferable, as it has carries the force of law and worsk to a stricter timetable.