It may seem off the cards due to their size and lack of empire. To become a superpower requires a nation to have significant political, economic, military and cultural influence. Britain still have a large amount of all of these things, holding a place in the UN security council and having the 7th largest military by expenditure. However, most of their influence comes from WW2, the commonwealth, colonies and other remnants of the empire. They are often in America's shadow. Here's some methods I've thought of: - Increased military arsenal; more battleships, submarines and more ships patrolling the seas. - Mandatory conscription system similar to Switzerland. - Investment into developing nations to encourage pro-British sentiment such as Canada and Australia. - Australian style immigration system. - Incentives for producing British media with distinct cultural value and distributing it around the world. - Anglicization to counter Americanization. - Increased funding to scientific institutions and the UK Space Agency and land on moon to become first man landed on moon. - Make use of overseas territories. - Invade and conquer United States of America. That should cover it for now.