The Domestic Abuse Act is clear that children are also victims of domestic abuse and this can be from witnessing abuse.  From this page you can download leaflets about supporting a child who has experienced domestic abuse.  The set of ten leaflets cover ages from baby to teenager and other related topics. 
These leaflets were reproduced for Cambridgeshire from the originals with kind permission of West Mercia Women's Aid
Embrace Child Victims of Crime have a Cambridgeshire based service offering free trauma-focused CBT and therapeutic counselling for young people.   The counselling is available to young people aged 13-19 (or up to age 24 with special needs) who have been victims of, or witnessed domestic abuse or sexual violence.  Referrals must be made by a professional but you can ask any professional working with you or your family to refer your child.  Children must be safe from the perpetrator of abuse for the referral to be accepted.
Family Action offer support to children, young people and families affected by domestic abuse.  They also offer support to families and children affected by domestic homicide.  You can download information leaflets below
Family Action also have a free Parent Helpline for confidential support and information Parent Helpline: 0808 802 0222

Open weekdays 6pm to 10pm, weekends 10am to 1pm Available for parents and carers across England.  They can provide emotional and practical support and guidance on all aspects of parenting