Apart from the label inside saying different sizes is there anything actually wrong with the shoes?
I can see one says size 11 but they are in fact the same size because I tried them on and they felt the same but just too tight for me, that's why I sold them.
To be honest with you, I bought them for £125 and sold them to you for less so I have already lost money. You can't expect me to give you £50 and for you to keep the shoes.
The dispute says if you want to be refunded then the shoes must be returned in the same condition that you received them but if you have worn them and removed the tags then they are no longer in new condition.