What form do I need to request an adjustment to a financial remedy order

Hello,

Not sure I'm in the right forum. I'm finally in a position to remortgage into my sole name. My FRO says I need consent from my ex husband as our daughter isn't 18 yet (the FRO says we both need to consent if we sell before then) he is entitled to 30% of the equity after all fees have been paid which is 20k. He is demanding 25k and doesn't want to pay any fees. I told him that's not what he agreed in the FRO in 2018 when he signed it. So he's refusing to sign. He said its because the house might be worth more in 2 years when our youngest is 18. But in order for him to get 25k, the house needs to increase in value by 20k. Also I'm 55 and managed to get an AIP with a 21 year term. I will be too old in 2 years to get the same deal and will forced to sell the house. We have a son with autism and I'm his carer. Losing his home would be devastating to him. Also, this house is the only inheritance our kids will get. I'm never going to physically see any money from this house. I'm just paying the mortgage so my kids have security when I die. someone told me that I could go to court and get an order for a judge to force him to consent to the remortgage now. Has anyone heard of this. Also there is a lot of history of abuse and other things he's done to be spiteful to me, including refusing to sign for a better interest rate with Santander so my repayments would be less. He doesn't contribute to an interest ything and our mortgage is interest only. Has anyone got experience of this or know which form I need to submit to court? I'm thinking an E2?