Ifonlyhewould - I don't know what your situation is regarding work. If you are working then make sure that you claim working tax credit. Unless you have a highly paid job you will be entitled to it. Also inform Child Tax Credit that you are now bringing up child alone and Child Benefit. Do this even if you are not working. If you go to your local Citizens Advice Bureau they can predict what your entitlements will be.
When I left my husband I automatically thought "Oh my god I will have to go to work full time, I will have to put my children into childcare". But a visit to the CAB informed me that in fact it was worth my while to work just 16 hours a week. If I had gone to work full time I would have gained £9.00 more a month, but my children would have had to go to a childminder after school. I was lucky enough to get a job where I finish at 1.00 and I am able to meet my children from school everyday.
I do know some single mothers who do not work at all and they cope financially. Don't think I could do it though - i'd go mad without the adult company of my colleagues at work.
Again I urge you to find out about private rent through you council/housing association.
Get all this sorted so that as soon as you do leave all you need to do is make a few phone calls.
Stay strong. One tip I have for you is to keep all the bad things about your husband in mind. It's easy to get emotional and weak. But for this period of time you need to feel anger and determination. Leave the emotional stuff for later. You can deal with that when you are safely distanced from him, physically, mentally and emotionally.