Blanch the cauliflower, carrots and celery in salted boiling water for 3 to 4 minutes. Drain, then transfer to a heatproof shallow bowl (do not shock in cold water as you normally would when blanching). Toss with the olives and cherry peppers. The warm vegetables will soak up some of the brine.
Combine the vinegar, 1 cup water, the sugar, 2 rounded tablespoons salt and the bay leaves in a pot. Bring to a boil, stirring to dissolve the sugar and salt, then pour over the vegetables. Let cool, tossing occasionally. Serve at room temperature. Refrigerate any leftovers.