In a small bowl, sift together the flour and bicarbonate of soda.
In a large bowl, combine the grape tomatoes, Roma tomatoes, shallots, onion, feta, mint, parsley, and oregano. Season the mixture with salt.
Add the flour mixture to the tomato mixture and stir until everything is well combined.
Pour enough vegetable oil into a large non-stick frying pan to reach about 1 cm up the sides. Heat the oil over medium-high heat until it is hot.
In batches, spoon 4 large tablespoons of the batter into the pan to form each fritter, flattening them slightly with the back of a fork.
Cook the fritters for about 2 minutes on each side, or until they are golden brown and cooked through.
Once cooked, transfer the fritters to a plate lined with paper towels to drain excess oil.
Arrange the fritters on serving plates, squeeze some lemon juice over them, and sprinkle with extra parsley.
Serve the fritters with tzatziki and additional lemon wedges on the side.
