Theres not much you can do until he goes back to work except keep on at the CSA who may eventually get you the standard £5 out of him.
One day your girls are going to have children of there own and understand that a good parent takes responsibility for their children, he'll have to do some fast talking to maintain there respect.
I suspect I could keep my ex living on the breadline for a very long time so he can avoid CSA payments and thats got to cramp his style especially with the ladies. If you can't beat them laugh at them.