As Ten says to Martha at one point, "Just walk around like you own the place. Usually works for me." There is some increased UNIT presence later in the show. For a while they dialed them back because the United Nations wasn't happy about being portrayed with a military arm or soemthing, but they figured out that if they called it the "Unified Intelligence Taskforce" then no one would complain. The Brigadier showed up once on the Sarah Jane Adventures, but not on Who so far.