In a clean mixing bowl, whisk together the gluten free flour, cornflour and enough sparkling water to make a smooth batter the consistency of double cream.
Heat the vegetable oil in a heavy-based saucepan until a breadcrumb sizzles gently when added to the pan. (CAUTION: hot oil can be dangerous! Do not leave unattended.)
Dip the shrimp in the batter to coat completely, then carefully lower into the hot oil.
Deep fry for 3-4 minutes, or until the shrimp is cooked and the batter is golden-brown and crisp.
Carefully lift out with a slotted spoon and drain on kitchen paper.
Season with salt and freshly ground black pepper. Serve immediately with sweet chili sauce.