I don't think it matters what 'evidence' is flying around, does it?
The NHS, via Tavistock, were asked to provide the evidence they kept and were working from, and were using to under pin their provision of treatment to children. The judgement was based on the Tavistock's own evidence of what they did.
Someone handing helpful evidence to the Tavistock now does nothing to change this fact; if there is relevant evidence the Tavistock should have had it and been working from it. What Mermaids and Stonewall and Maugrim and anyone else thinks is irrelevant, unless they were working in the Tavistock, setting policies at the time. If it's the case that they're this involved because actually they were, then it's a whole other issue of why people with a lot of politics and personal agendas were involved in medical decisions they had no qualifications in, whether this involvement has influenced the practices the Tavistock has been taken to court over, and if so, why the qualified professionals permitted this to happen.
Appealing against the NHS having to obey the law, and stop carrying out experimental treatments on children? Seriously?