Have you divided your finances yet, have you got a Consent Order?
Other factors of SM include each of your potential earnings, for example if you didn''t work but could (no disabilities) or if you were in part time work - could you increase your hours etc.
Also your children are older (as CTC is close to ending) I''m presuming you don''t need childcare to enable you to work.
I think what a Court would look at is to enable each of you to continue your life independently - they look for a Clean Break. In some circumstances, this can not be achieved, so an equalisation is looked at. This is where SM comes in, usually where there is a big difference in incomes.
Prob best to wait for LittleMrMike or Dukey to come along and give you proper advice.