Buying Ex out of Mortgage (England)

Morning all,

I purchased a house with my ex in 2023. Soon after, we split up and police ordered him to leave the property. Ex has made less than 12 months payments for the mortgage. I haven’t had a penny from my ex since then, I’ve had to pay for multiple house repairs (Most costly was the roof) and the full mortgage payments on my own.

Ex put in 9k deposit to the house, I put in 27k. Ex is now threatening to go to the courts to force a sale of the house unless I buy him out. Remortgage is due August next year but he’s saying he’s not prepared to wait til then. I was under the impression there’ll be additional fees/costs if I remortgage early so I want to avoid that. We’ve had limited communication during the last few years but I’ve always said I’m happy to buy him out with his initial deposit he’s put in (9k). He’s asking for 15k based on the bills he paid whilst he was shortly living at the property and the value of the house going up.

I just want some advice on what to realistically expect, I understand morals and the law are two different things but will his 3 years of missed mortgage contributions come into account or not? We’re joint tenants.