Unexpected parent SKU for this child SKU. For help on how to proceed, see http://sellercentral.amazon.co.uk/gp/help/23721
This error occurs when processing your data would change the ParentSKU that is associated with a child product. Before a child product can be related to a new parent, you must remove that child product from its existing parent-child relationship.
To eliminate a relationship, you can delete either the parent or child product. When you delete a parent, you remove the relationship between that parent and all its children. When you delete a child product, you eliminate the relationship between just that one child product and its parent.
After you remove the original relationship, you can re-assign the child product to a new parent product.