I sold an item and had put in the description 'slightly discoloured'. Buyer has come back requesting return as it is heavily discoloured which they say was not mentioned in the description or shown in the photos. I'm not very happy but am wondering do I return full cost (bid cost plus postage plus the return postage), so more than was actually paid? How is best to proceed with this as I know these things never go to the sellers way. Never had this before.