Bring champagne, 2 cups sugar, tea, and 6 cups water to a boil; reduce heat, and simmer 10 minutes. Add peaches; simmer gently for 5 to 20 minutes (knife should insert easily into peach). Let peaches cool in liquid, 3 hours. Peel peaches; slice 2 into eight sections each. Set aside remaining peaches. Strain liquid. Chill 2 cups liquid. Sprinkle gelatin over cold liquid; let stand to soften, 5 minutes.
Meanwhile, bring 2 cups liquid to a boil. Add to gelatin mixture; whisk to dissolve gelatin, about 5 minutes. Pour 3 tablespoons of the mixture into mold to coat the bottom. Cover; refrigerate 30 minutes, until just set.
Combine remaining 1 1/2 cups sugar and 1 1/2 cups poaching liquid in a skillet; bring to a boil, stirring to dissolve sugar. Reduce heat; let syrup simmer. Halve plums, and remove pits. Add plums, cut sides down, and poach until skin loosens, 5 to 10 minutes. Remove from syrup; let cool. Remove skins. Slice each into four wedges. Chill.
Arrange plums over gelatin in mold. Add 3/4 cup gelatin mixture. Cover with plastic; refrigerate 45 minutes, or until set. Add remaining gelatin; arrange peach slices on top. Cover with plastic; chill until set, 6 hours.
To unmold, dip mold briefly into hot water, and run the tip of a knife around edge. Invert onto a platter. Cut reserved peaches in half, discard pits, and serve with gelatin.