Data sharing with a parent I do not have an agreement with

I am a coach - working with a 11 yr old remotely. Need legal guidance on Data sharing and confidentiality compliance ICO
recieved conflicting legal advice about sharing the full notes
Parental harassment and veiled threats - sent C+ D letter
Being brought into a parental conflict and dissolving myself within the dispute as best navigated as possible. Looking for legal advise from a lawyer who is insured and can write on letter head if need be for future correspondence to represent me. So far I have outsourced freelancers who have edited my documentation but I have sent myself.
Looking for UK legal and lawyers specialising in UK based in the UK please.