Basically in the title. I moved out with effect on 17/7/2023 after returning the keys to the landlord. She is refusing the refund of my deposit as she stated that the mattress has a stain under the matress protector. I only discovered of the stain when I moved in and as such retained the protector but didn't communicate this as I thought she was aware of this. Do I have any recourse if she refuses repaying my deposit? Also you can buy a whole bed from ikea for way less than the deposit due, should such claw backs contain a element of reasonability.

Update 24/7/23: Thanks for all the assistance. The landlord refunded my deposit this afternoon in full.