Non-appeal certificate

My ex-husband and I brought a house together in Charente , when we were madly in love and signed ‘en-tontine’ (yes, hindsight is a wonderful thing😢)

10 tears later, We got divorced in a UK court, who gave the final judgement with financial orders, including that he should sign the house over to me and would be responsible for all bills and taxes until he did so.

This is where it gets complicated, so I apologise in advance☺️ we are both UK citizens, however he lives and works in Sultanate of Oman. He is a financial advisor and has never complied with the financial court order, despite us trying to enforce it.

Earlier this year, I received a French court order from him trying to sue me for €20,000 allegedly for repairs to the roof, for which I had no knowledge of.

I have engaged a French lawyer, we are disputing  this,  and my lawyer thinks we should now go for enforcement of the UK judgement via the French courts, however I have to supply a non-appeal  certificate for submission to the French courts. Does anybody know how I go about getting one, as this is not a document that is used in the UK legal system.

Thank you so much for taking the time to read this, I really would be grateful for any advice