To prevent a soggy bottom its always best to blind bake a pastry, particular if you are adding a wet filling. To do this line the pie dish with the pastry then prick all over with a fork. Line the pastry with a scrunched up piece of baking paper. Weight down the paper with dried pasta/baking beans. Bake for 10 minutes at 200°C Fan/400°F, then remove paper and bake for a further 5 minutes.