CMEC use a formula to assess the level of maintenance payable and these produce predictable and consistent results which leave little discretion in calculating the maintenance. There are some allowances made such as the cost of travelling to exercise contact etc. There are still some areas where the courts have jurisdiction for making decisions on such as children between the ages of nineteen and twenty-five who are undergoing suitable fulltime education or where one parent lives abroad. School fees are also an area in which the court still has jurisdiction.
There is a link to the Child Support Agency website which has a calculator into which you can input information in to, to then ascertain the likely level of maintenance that would require to be paid and which you might find helpful.