Hello and thanks for your question.
Your daughter must report the harassment to the police immediately. If the previous injunction she had against her ex has expired, then she should apply for a fresh injunction.
If the arrangement for him to see the children was via a court order, then she needs to take the case back to court to get the court order changed, so that he only gets to see the children in a way that is safe for the children and safe for her - if indeed the children still want to see him.
The court form to apply for a child arrangements order or to amend an existing order (if the old court case has ended) is C100. If the court case concerning the chidlren is still ongoing, then she needs to apply on form C2, to change an existing order, or just to get another court hearing so that she can update the court about this man's behaviour.
Here are the forms:
To apply for a non-molestation order (also called an injunction), she needs form FL401, here:
If her ex has breached the terms of an injunction that is still in force, then that is a criminal offence, and she needs to tell the police immediately.
If the harassment she is currently experiencing is bad enough, the police can treat it as a criminal offence straightaway, even if the old injunction has expired, without her having to go to the family court again.
Women's aid can help her with going to the police, and, in an emergency, they can find her some temporary accommodation if she has to get out of her own home fast because of credible threats made by her ex.
They have a 24 hour free tel no: 0808 2000 247 and their website is here:-
Your daughter could do with some urgent face-to-face legal advice as well - here's where to find a specialist family law solicitor:
I hope this helps and I wish you and your daughter the best of luck.
Thanks and best wishes...