Set 4 strawberries aside in the fridge until you are ready to serve. Slice the remaining strawberries. Combine ½ cup sugar, lime juice and 1 tablespoon water in a medium non-stick saucepan. Bring to simmer, stirring to dissolve the sugar. Simmer gently 1 minute. Remove from the heat. Add sliced strawberries, shake the pan gently to coat. Cool 15 minutes.
Using a slotted spoon, spoon the strawberries between 4 x ¾ cup-capacity (185ml) glasses. Refrigerate until required. Pour the syrup into a jug and refrigerate until ready to serve.
Pour 100ml of cream into a medium saucepan. Sprinkle over the gelatine. Whisk gently over low heat until the cream is warm and gelatine has dissolved (do not boil). Add the remaining cream, remaining ½ cup sugar and vanilla. Whisk gently over low until sugar has dissolved and mixture is warm, do not boil. Remove from heat and stand 5 minutes. Whisk in yoghurt, then strain into a jug.
Pour panna cotta mix over the strawberries, cover and refrigerate 4 hours until set. Just before serving, hull and slice reserved strawberries, arrange over panna cotta. Spoon over reserved strawberry lime syrup. Serve with lime wedges.