M&S Prawn Cocktail A British classic of succulent, cold-water prawns in a creamy Marie Rose sauce, infused with brandy. Gluten free. Ready to eat. Serves 2. Our M&S seafood products have been sourced from fisheries and fish farms in a way that minimises their ethical and environment impact, while guaranteeing you the highest quality, delicious seafood you’d expect from M&S.