Preheat oven to 180 °C (350 °F).
Combine all salsa ingredients together in a bowl. Season to taste with salt and set aside.
Pat fish dry with paper towels and remove any remaining scales or bones. Cut into large 2cm-thick fingers. Combine flour, Mexican spice and salt in a dish; coat fish well in the flour mixture, shaking off any excess. Dip each piece of fish in egg then coat in panko bread crumbs.
Heat oil in a large fry-pan on medium heat. Cook fish in small batches for 1-2 minutes each side, or until just cooked through. Set cooked fish aside.
Warm taco shells in oven according to packet instructions (usually about 5 minutes at 180°C).
To serve put salsa, chopped veggies, fish, guacamole, greek yoghurt and taco shells in the middle of the table and let everyone build their own.