Those mild-mannered shopkeepers and their well-tended establishments at Epcot's United Kingdom Pavilion are now embroiled in a world of secret agents, mystery, and an evil plot to turn the whole world into one giant golf course. So that explains what those kids, Ellen and Faye Meadows, were doing crammed in a phone booth playing with cell phones. Was that a golf ball that just popped out of the pay phone's change return? A clue! Sleepy little areas in Epcot's World Showcase are coming alive with high-tech intrigue, as young heroes such as Ellen, 9, and Faye, 7, of Hemel Hempstead, England, run around trying to save the world, playing a prototype, high-tech, adventure game that Disney researchers are testing.