http://www.csa.gov.uk/en/contact/
there is how to contact them
How much they charge the parent depends on how much they earn.
Any income (whether through csa or private arrangement) is taken into consideration when applying for means tested benefits
Is the person on the birth certificate the dad? if so, why would you want to take it off? does the dad want contact? Although maintenance and visitation should be seperate issues, are you really saying you want the father to pay for the child, but not allowed to be aknowledged as the father OR see the child or have any contact with them? I cant imagine anyone swallowing that to be honest!