Hello, I'm back and want to thank you all so much for responding.
I've spoken to Women's Aid this morning, and they were really helpful. I have some telephone numbers for legal advice etc.
I don't know what will about the police, and if they will come back. I'd imagine there will be an automatic social services referral. After some consideration, I've decided that I would welcome a bit of help from social services, and I'm going to ring them myself on Monday morning, and ask what the best thing to do is in order to safeguard my children.
I thought long and hard about whether or not to allow DH to come back this morning (he went to his parent's house as they are away and he has a key). The children were asking for him, and were upset this morning. He is here now, and I have come upstairs to lie down for a bit as I need some head space and only got three hours sleep last night.
DH is back on the understanding that this becomes a completely teetotal house. Being cynical, I know that he will now be on his best behaviour for a bit, which gives me enough time to decide where we go from here.
I know that I wound dh up last night, and was argumentative. I am not at all proud of myself, and part of me feels I deserved what I got. Still, I know that a line has been crossed here, because he hit me in front of the children (and that's why I called the police, despite my own part in the argument, because I want ds1 in particular to know that this is not okay, and that there is never any excuse for it). He has hit me before, infrequently but a fair few times over the past couple of years, always when he had been drinking, but never in front of the children before.
I know that unless I prevent my children from witnessing domestic violence, then I am complicit in failing to safeguard them. This is why I'm going to call social services myself tomorrow and ask for advice.
I'm sorry this is rambly, but I am feeling very odd this morning. I think I am probably in shock. I just wish none of it had ever happened!
Thank you for saying that I did the right thing in calling the police. I think I would be doubting myself if I didn't have that reassurance. I feel like I've started something that I can't stop now - but I've known for a while that some sort of crisis was going to come sooner or later, and I would have to stop sticking my head in the sand and do something.