Whenever you are making the case for less or more contact, stress the ways in which this is what is best for your child, always put their needs in relation to contact before yours.
If you are in dispute with the father about him having contact with your child, make notes on every contact visit e.g. if he arrived on time, and how the child was when she/he returned e.g. clean, fed, happy, distressed, crying, scared. Note how the child/ren behaved before and after and what they said about the visit.
Ask other witnesses to do a statement. If anyone sees children before and/or after the contact with the father and notices how the child is, ask them to put it in writing. Any observation from a witness can be helpful.
If your children live with their father or other relative under a Child Arrangements Order and you want more contact and/or unsupervised contact, you can apply to the court to change the contact arrangements .
If a parent ignores or changes the Court Order you can apply for an Enforcement Order  and there will be a court hearing where you say what has happened and that you want the Court Order to be enforced.
If you are worried that the father might take the children out of the country or even away from your care you can apply for a Prohibited Steps Order .