Grease two 2/3-cup (160ml) capacity moulds. Place the milk in a microwave-safe jug. Heat in microwave on HIGH for 20 seconds or until hot.
Sprinkle gelatine over 2 tablespoons boiling water in a small heatproof jug. Stir with a fork until gelatine has dissolved. Stir gelatine and sugar into hot milk until sugar dissolves.
Combine cream and milk mixture in a jug. Mix well. Divide the mixture among prepared moulds and cover with plastic wrap. Refrigerate for 6 hours or until set.
Lightly spray a large non-stick frying pan with oil and heat over medium heat. Cook peaches, cut side down, for 2 minutes, then turn. Combine brown sugar, juice and 2 tablespoons water in a small bowl. Pour over peaches and bring to the boil. Simmer for 1 minute or until sauce thickens slightly. Remove from heat, and set aside to cool.
Dip each panna cotta mould briefly in a bowl of hot water and turn the panna cottas out onto serving plates. Serve with peaches and drizzle with syrup.