Useful links:
https://www.youngminds.org.uk/young-person/blog/five-things-you-can-do-if-someone-tells-you-they-are-self-harming/
https://www.youngminds.org.uk/parent/a-z-guide/self-harm/
National Self Harm Network Forum
https://www.nshn.co.uk/
Distractions that can help
https://www.nshn.co.uk/downloads/Distractions.pdf
Making a safety plan for home