Ex wife set the CSA on me; what should I do?

I agreed in principle to my Ex wife following divorce that she could keep all benefits for the children as she needed them to obtain her mortgage – I found that she wasn’t happy with just that and set the CSA onto me. I have 50/50 shared care of the children and have to provide exactly the same as she does – school uniforms/lunches/activities etc.

The CSA told me that they prefer in shared care situations for the parents to sort things out between themselves – my money motivated ex wont discuss anything. I now wish to claim the child benefit for the children as I cant manage if she is to have all benefits and CSA money (£270/month). Have there been many success with trying to get child benefit from ex wives whereby 2 children are involved? 1 claim each?

How easy is it as I know my ex wont want to give it up. Is it as simple as filling in an application form and letting the DWP sort out who gets what?