I am quite up to speed with this and advise you to go to the CSA YOURSELF. They allow you certain things, and dissallow others but unless you earn a LOT of money you will NOT be paying what you pay now mate, i am confident of that much.

Biggest advice i can give you, and i know its been covered, but ENSURE you can prove every payment you have ever made pal, dont EVER pay cash as they couldnt give a flying fuck what you tell them, or even what she tells them, they will hammer you for back pay to the penny. Yes, been there, done that.

I recall their new website was pretty damn usefull, allowing you to work it out yourself using the exact software they wil use, it was certainly accutae for my own claim, so i think its worth an hour on, just ensure your thorogh with your numbers and dont guess anything.

Best of luck pal.