1. In a large mixing bowl, combine first three ingredients until smooth; reserve 1/4 cup for dressing.
2. Add fish to bowl and toss to coat; marinate for 15 minutes.
3. In the meantime, line a baking sheet with aluminum foil and spread fries over half. Place in oven and bake at 400 degrees Fahrenheit (200 degrees Celsius) for 10 minutes.
4. Place cornflake crumbs in a large shallow dish and dredge fish in crumbs until fully coated.
5. Remove baking sheet from oven and line fish fillets across the empty half of the pan. Return to oven and bake an additional 20 minutes.
6. While fish bakes, slice off tops of pita. Toss together tomato, cucumber, and pickles.
7. Divide fish, fries, and vegetables among pitas and drizzle reserved dressing over each.