Child maintenance?

Okay so my ex has turned pretty nasty, domestic violence and stuff. Social services are getting involved for when my baby is here, police have been involved, flagged my house for my safety etc. I'm wondering about child maintenance, I know he won't willingly pay me every other week or month or whatever, because all he seems worried in is splashing the cash out on drugs, alcohol, new bike parts and wasting money on new clothes, £106.00 wasted on 3 items!? Crazy if you ask me, considering there's me over here, cutting daily things off, like going out for lunch, just to save as much money as possible. I've come across the child maintenance service. Does anybody know anything about this? Does my ex have to accept the offer of him paying? And if he doesn't pay should I still let him see the baby(that's if social services give him any access at all) I'm not sure on what to do for the best here. Any advice would be greatly appreciated :)