Preheat the grill to high. Put the sausages on a tray under the grill and cook for 10 minutes, turning regularly, until cooked through.
Meanwhile, bring a large pan of water to the boil. Add the halved baby potatoes and simmer for 10 minutes until cooked. Add the peas and broccoli to the pan for the final 2 minutes of cooking time. Drain.
Meanwhile, whisk the olive oil, vinegar, honey and mustard together in a small bowl. Stir the dressing through the drained potatoes, peas and broccoli. Garnish with the cress and serve with the sausages.