From wiki..............
In the United Kingdom, membership is restricted to certain groups only. Trade membership is available to the owners or managers of businesses for £20.00 (plus VAT). Trade members receive a complimentary spouse/partner card, and can purchase additional cards (at a cost of £12+VAT each) for employees. Qualified professionals, such as solicitors, magistrates, accountants and engineers, as well as employees in certain specific sectors (such as medical services, education, local government, the civil service, airlines and banking) may apply for individual membership, which costs £25 including a spouse/partner card. While these restrictions are posted in the store they are not applied rigorously; in reality any individual may apply for, and receive, a membership card.[31] A Costco card issued in another country is valid in the U.K.,[32] and as such, it would be possible for a U.K. resident to sign up elsewhere and use their card at home without meeting U.K. membership requirements