OP if you feel unsafe or in danger call the Refuge national helpline - 0808 2000 247 the line can often be [is usually] busy, but if you leave a message, they do call back.
They can then look up refuges in your area where you can go, and put a stop to it all; you'll get emotional and practical support. If you needed to go in the evening, call around 10am in the morning.
I don't know how it works afterwards with access to your child, but you would get support there.
In terms of reporting, I made a statement about my DP to the local police and asked for it to be recorded but not officially acted upon; I didn't even want to give his name, but did in the end, so it is on record somewhere, and I received a police reference number, which made me feel safer that at least his behaviour was being noted somewhere.
If you feel the national women's aid couldn't help you sufficiently, try searching for the number for your local outreach service.