Sammiejane - your DH's ex and mine could be twins. DSS (16) will not be returning to school next year and will be working so he is no longer the cash cow that his mother requires, so you can bet your "A" that he will no longer be living with her.

With regards to writing things on calendars beware! We had an informal shared care arrangement. DH wrote down all times that the kids stayed with us, what essentials we had to buy them (shoes/clothing etc). He submitted this to CSA. CSA wrote a letter to the ex and she disagreed with the number of days that we had them. CSA took the ex's word for it and DH basically got a "too bad, so sad" letter and had to continue to pay full maintenance.

I agree with N2L - get a parenting order!