Several coupon codes for britishmuseumshoponline.org are available. One can get an instant 20% off storewide discount code by joining The British Museum Shop's Email Newsletter. There's also a free UK standard delivery on orders over £100. Additional codes offer an extra 20% off sitewide with a minimum purchase, and up to 40% off antiques with competitor codes. There are also specific discounts like 20% off the Peru: a Journey in Time Exhibition and 30% off the Arctic Range. Please note that these codes are subject to terms and conditions and may require a minimum purchase or apply only to specific items. Always check the validity of the codes before using them.