I'm planning my decor. To that end, I need to the approximate height of a few sets:
From the pages you linked, under "specifications":
Dimensions – This buildable model measures over 15 in. (39 cm) high, 11.5 in. (30 cm) wide and 9.5 in. (24 cm) deep
10289 Bird of Paradise
As a guide, the tallest leaf limb measures over 18 in. (46 cm) high and the flowerpot measures over 5 in. (13 cm) in diameter.
10313 Wildflower Bouquet
Dimensions – The stems come in a variety of lengths. As a guide, the ‘larkspur’, with its straight stem, measures over 18 in. (47 cm) tall
10280 Flower Bouquet
The stems come in a variety of lengths. As a guide, the ‘snapdragon’, with its straight stem, measures over 14 in. (36 cm) high.
Don't forget that putting the bouquets in a vase adds a little bit of height, while at the same time lowering the height a little because the flowers spread out.
Generally it's probably easiest to assume ~50cm for each set when planning.