@Needlenardlenoo apologies for dumping all that on the thread! It has been a long day. It is never-ending at the moment.
Have you thought about a Direct Access Barrister? I can recommend Alice De Coverley. I haven’t used her personally, but I know people, including some MN’ers, who have. If I needed a barrister (including if I only needed advice or paperwork support rather than full representation), she would be my first choice. She is at the top of her game. Well regarded by parents, the courts and government alike.
Direct Access Barristers don’t hold your hand in the same way as solicitors do. For example, they will tell you when you can do something yourself, which is no bad thing. You are capable and educated, so a DAB will be fine. The benefit is they are cheaper than a solicitor.
If that isn’t something you want to consider, you could see if SOSSEN has capacity for 1:1 work. (Or using their grounds of appeal drafting service as I think that may be what you mean by Tribunal bundle.)
The above is with the caveat that if it is a choice between paying for support and paying for independent assessments, you should choose the latter. The best representation in England can only work with the evidence available.