Reserve 24 cherry halves for serving. In a blender, combine remaining cherries, oil, capsicum, chilli, garlic, vinegar, paprika, 3/4 tsp salt, 1/4 tsp pepper and 1/4 cup ice. Blend until smooth and strain through fine-mesh strainer into a bowl. Season to taste with salt and pepper. Chill for 30 mins or until cold.
Reserve green tops from fennel. Using a mandolin or sharp knife, carefully shave fennel bulb into very thin slices.
Cut cucumber into medium dice, cutting around seeds. (Alternatively, using a small melon baller, cut round balls from cucumber.)
Chill 8 small shallow wide bowls or salad plates. On each chilled plate, mound shaved fennel into centre. Top fennel with prawns. Pour some vinaigrette around prawns and garnish with cucumber and reserved fennel tops, if using. Drizzle with extra oil. Sprinkle sea salt and grind black pepper over prawns. Serve immediately.