The Maudsley charity have produced some wonderful supportive resources, entitled 'Families Under Pressure' which include tips on helping children with difficult behaviour and negative emotions. You can find short videos and top tips at;

https://maudsleycharity.org/familiesunderpressure/

Nip in the Bud works with mental health professionals to produce short films and fact sheets to help parents, primary school teachers and others caring for and working with children to recognise potential mental health conditions. The goal is to increase the prospects of early intervention and to reduce the risks of those conditions becoming more serious in later years.

The films cover Anxiety Disorders, Attention Deficit Hyperactivity Disorder (ADHD), Conduct Disorder, Depression, Obsessive Compulsive Disorder (OCD), Post-Traumatic Stress Disorder (PTSD) and Autism Spectrum Condition (ASC). 

https://nipinthebud.org/