Parki peed on our leather seatee a few weeks ago when OH forgot to bring her litter tray in. After the initial panic did some research and found a product called Petweeaway. Had nothing to lose so sent away and am so happy as I found it works.
It removed the stain and odour from leather. Also use on kitchen floor when Archie pees out of his tray.
You dilute it so it goes along way and it states its a natural product.