How to prove Mental Illness ?

[internuk]

Ex wife recently claimed I suffered narcolepsy and was suicidal (both totally false allegations), to stop my midweek visit by our 6yr old son. She refused to reinstate visit after I provided specialist evidence totally refuting her claims. Last week, she tried cancel my saturday visit by our son, on same grounds, which would totally exclude me from him. I took her to Family Court for more access to our son AND because she was neglecting and abusing him. Court wouldn't reinstate midweek visit "at the moment", but left saturday visit fixed. (No court order yet.)
I've never been divorcing before, so don't know who controls visits. Have run out of money for legal advice and tried legal aid (which I think she has, on grounds of MY abuse to her, which has never happened) but I was refused, despite divorcing her for physical violence and mental abuse against me.
Ex then made very serious and totally false allegations against me at court, (not heard so far) but they could never be proven as never happened.
I sincerely believe she is mentally ill and would like to know how I can pursue that ?
NSPCC/Child Protection/Police already involved re her violence to our son, now CAFCASS involved for Child Impact Analysis Report. Factually, I have brought up our son almost entirely without her and she always stated she'd leave him with me ... then took him to get max money out of me from settlement. She has never wanted him and still doesn't. I went to police a few days ago, purely to ask what would happen if I felt our son was 'at risk of harm' and kept him with me, rather than return him. I was advised to do this by Child Protection if worried. Police (and others) all very helpful, but have now interviewed me, her and our son. (Who wants to live with me, not her.)
Seems she can claim what she wants and get away with it, but I'm at risk of losing my son. She IS mentally unwell, so how can I claim that or prove it at court next time ? (In August.)

[charitynjw]

But there may be times when there are sufficient concerns about your mental health and your ability to make use of the help offered.

In these circumstances your relatives or the professionals involved in your care can ask for a formal assessment of your mental health through the Mental Health Act process.

Your nearest relative has the right to ask the local approved mental health professional service, which may be run by local social care services, for an assessment under the Mental Health Act.

https://www.nhs.uk/using-the-nhs/nhs...al-health-act/