The BBC is listened to by over 120 million people every day. These large stations also have relay stations all over the world, helping provide a consistent and strong sound. That BBC broadcast from London you are listening to may have actually be relayed from a station in Canada, which pickup the broadcast from a satellite. As a result, the big stations are very easy to pickup. The BBC can often be heard on night on these FM stations using your car radio.
Many large stations rely on immense power for signal broadcasting.
Your local AM station usually uses 5,000 to 50,000 watts of broadcasting power. A shortwave broadcasting station may use 1,000,000 watts for each signal generated. Well, President Gorbachev listened to the BBC and Voice of America news during the few days of the overthrow plot in the former U.S.S.R. President Bush, despite all the information available to him, still listened to shortwave radio news in the evenings. You can listen to news from around the world, propaganda, music, religious broadcasts, sporting events, etc. In short just about anything.