You’re not protected by Section 75 for credit card purchases for items under £100 but you may be able to request a refund from your credit card provider under the Chargeback scheme if you’re unable to get a refund directly from the retailer.
Chargeback covers debit and credit card purchases, but unlike Section 75, it’s not legally binding. Your credit card provider may or may not subscribe to the chargeback scheme. If they do they may, based on the evidence you provide, attempt to get a refund from the retailer’s bank, but there is no guarantee that your claim will be successful.