Place all the ground spices, garlic and coriander in a mixing bowl. Toss the chicken in the oil, then add to the spices and toss to coat lightly in the spice mixture.
Make the salsa, mix the tomatoes, coriander and cucumber in a bowl and drizzle over the oil. Transfer to a serving bowl.
Make the guacamole, mash the avocado with the lime rind and juice and sweet chilli sauce, if using, until soft and rough-textured. Transfer to a serving bowl.
Heat a griddle pan or heavy-based frying pan and cook the chicken for 3–4 minutes, turning occasionally, until golden and cooked through. Fill the tortillas with the hot chicken slices, guacamole and salsa, and fold into quarters. Spoon over a little soured cream, if liked.