Heat oven to 175 degrees celsius.
In a large bowl, combine sugars with peaches and toss gently. Cover and let stand for 1 hour.
Line a pie plate with bottom pastry. Trim edges evenly then set aside.
Separate the juice from the peaches.
In a small saucepan, combine the cornflour, nutmeg & cinnamon. Gradually stir in reserved juice. Bring to a boil then cook and stir for 2 minutes or until thickened. Remove from the heat and stir in lemon juice and butter.
Gently fold in peaches. Pour into crust.
Roll out remaining pastry to make a lattice crust. Trim, seal and flute edges. Cover edges loosely with foil. Bake for 50-60 minutes or until crust is golden brown and filling is bubbly. Remove foil. Cool on a wire rack.