Court application: who pays for what

Hi - I’m hoping that I could get advice on how I apply to court to get direction on who pays for what please
I give ex-wife £10,400 a year for one child. She flatly refuses to pay for school lunches, music lessons, extra curricular activities, school trips, clothes. I’ve asked repeatedly, suggested discussing it by email/phone/mediation but she just says stop these “malicious” communications.
Is there a way of applying to the court for order fir who pays for what pls? If so any idea what form I should fill in? Many thanks

The way I understood it was the parent “With care” pays for everything, and the other parent pays maintenance.
The parent with care is the one the child resides with most of the time.
You can always come to your own arrangement? I.e. you pay the fixed CMS rate, but offer to pay for extra after school stuff?
I think your query is though that you are paying 10k a year and expect these extra things because of the amount?
Look at it from the other parents point of view, do they have to work? Pay mortgage, rent so your child has a comfortable home? Maybe your contribution only covers this?

Hi - thanks very much for taking the trouble to reply which I appreciate very much. I pay the £15,000 a year school fees, £10,400 cms and she re-married. She doesn’t work and refuses to pay for anything for our youngest son. My oldest son is at university and I’m struggling to support him as well. Also parental alienation - but that’s a long story!

Yeah sounds like a complete nightmare.
I’m on the other end of the scale....ex pays CMS £30 a MONTH, self employed (Gets away with murder) and I pay for everything D