DO NOT tell him your leaving. DO NOT leave your children with him. I have worked with domestic abuse survivors for a number of years and I can tell you that a) leaving the relationship is the most dangerous time for women and children and b) if you leave the children behind he might keep them from you and you will have to go to court to get access to them.
Contact women’s aid. Get them to help you make an exit plan. Gather all important documents, passports, drivers licenses, birth certificates, bank stuff, etc. Keep them together somewhere safe where he won’t find them. Ideally leave them with a trusted friend or family member.
Contact your local council and housing associations. Tell them you need to flee domestic abuse. Tell them that you have your children with you. They will have to house you as a priority and they keep a certain % of housing stock for exactly these purposes. You can apply to anywhere in the UK.
Contact the children’s schools and make them aware of the situation and that Dad is not allowed to pick them up from school, nor is your new address details to be passed on to him once you have moved. They will support you and the children through this.
Your other option is, depending on your housing situation, is to go to court and get an occupation order to allow you and the children to remain in the home and your DH will have to leave. Once you obtain this you change the locks and install a ring doorbell or similar. Keep the doors locked and if he comes to the property, call the police. DO NOT answer the door. Have him arrested any time he comes near you or the property. Then you can apply for a non mol to keep him away from you.
It’s a lot to take in and to go through, that’s why contacting women’s aid should be your first action. They will support you and give you the best advice. They can also put you in touch with the best lawyer in your area who have had good outcomes for their clients. They can also help you with sorting any benefits you may be entitled to.
Well done for making the decision to leave. You’re doing the right things.