EplusNINE is a showcase site. Buying happens with the retailer you are directed to, and that retailer's refund policy applies to your purchase.
If you wish to return a product, please contact the retailer directly and follow their returns procedure. Most online retailers in the UK accept returns within 14 or 30 days.
Your UK consumer rights apply to any online purchase. Check the retailer's policy for the specific terms that cover your order.