If you can't afford the court fee to submit a C100 application for Child Arrangements, there is a fee remission option, for those on benefits - so you don't have to pay the fee. It may be available for others on a very low income, even if not on benefits and if you're not entitled to the fee remission you may still get some money off the fee, if on a low income. The application form is EX160. You should be able to tell if you're eligible from the application form questions.