Preheat the oven to 350 degrees. With the 3 Tablespoons cold butter, butter a 9 x 13-inch or baking dish and sprinkle bottom with 2 Tablespoons of the sugar. Set aside.
In a large bowl, whisk by hand the eggs and yolks. Add 3/4 cup of the sugar and continue to whisk until thoroughly combined. Add the orange juice concentrate, half and half, 1 cup of the heavy cream, 3 Tablespoons of the orange liqueur, orange and lemon zest, vanilla and salt. Whisk 1 minute.
Lay the bread slices on a flat surface and butter one side of 4 of them with ¼ cup of the butter. Spread half the jar of the marmalade on the other 4 slices of bread. Place the buttered bread slices on top of the marmalade slices, with the butter and marmalade on facing the inside, just like making Paddington himself 4 of his favorite marmalade sandwiches!
Cut each sandwich into large 2-inch cubes and place half the cubes into the prepared pan. Pour half of the egg mixture over the bread cubes in the baking dish, allowing it to soak in for 15 minutes.
With half of the remaining marmalade, drop 4 spoonfuls on top of the soaked bread cubes and top with the remaining bread cubes. Pour the other half of the egg mixture over the top, allowing it to soak in 15 more minutes. Drop the remaining marmalade over the top and swirl in with a knife gently. Sprinkle the remaining granulated sugar over the top.
Bake for 45 minutes, or until a knife inserted in the middle comes out clean. Let the bread pudding cool for 10-15 minutes before glazing.
To make the glaze, in a small saucepan melt the remaining 4 Tablespoons butter on medium high heat. Remove from heat and add powdered sugar, the remaining 2 Tablespoons orange liqueur and remaining ½ cup heavy cream. Whisk until smooth. Drizzle glaze over the top of the bread pudding and serve. Cover any leftovers with plastic wrap and store in the refrigerator.