Battery refund

I bought a car which was suppose to be cleared with the police. That was not done, Brian took the car back to do that police clearance, and when he brought the car back, it was leaking oil and water. I refused to take it. And eventually after a fight with Brian, I was refunded for that car, however there was a new battery that my mechanic replaced, and I have sent them an email and also told Brian that there's a new battery in the car when he took it. Now I'm asking that they give me back the new battery and take their old or refund it, I'm being given a ru around again. Brian tells me that I should have claimed for the battery when they refunded me the car money. So much was going on and because that battery didn't belong to me but my mechanic, I forgot about it, reminded them a week after they refunded the car. Now they are making that an issue, I need the battery back or refunded. I also have an email informing them about the battery, first day they took it back. I would not recommend