For the dressing, combine the white wine vinegar, horseradish and lemon extract in a mixing bowl and stir to combine. Whisk in the olive oil and season to taste with salt.
Bring a large pot of water to the boil. Set up a bowl of ice water next to the stove and set a colander inside the ice water (so no ice is inside the colander). Stir a little salt into the water.
Add the vegetables in separate groups to the boiling water and cook each batch until just tender, about a minute; each vegetable should still have a little snap. Leave all the vegetables to cool and mix in the ice water after cooking.
Drain the vegetables well and pat dry. Add the cooked vegetables, radishes and cucumber to the bowl with the dressing and toss well to combine. Season to taste with salt. Transfer to a platter and garnish with the dill and mint or pea tendrils.