Your options:
First, use eBay/s money back guarantee to get a full refund. The seller will be required to send you a prepaid return label if he wants the remaining skin patches back. See: https://pages.ebay.co.uk/ebay-money-back-guarantee/
If the seller is registered in the UK you can also report them to trading standards. (You will need to keep some of the patches back to show them, also the label). If you bought these direct from a seller in China, they are outside of UK laws and there's little you can do.
Remember that buying from unknown sellers on eBay is not like the shops. For health or skin care products, be careful only to buy from a known reputable UK supplier.
