1. For the marinade: In a blender, combine the olive oil, chilli powder, Worcestershire, cumin, red pepper flakes, garlic and lime juice. Next add the sugar, salt and pepper and blend the marinade until it's totally combined and smooth.
2. For the meat: Place the chicken and beef in separate 2-quart baking dishes or large resealable plastic storage bags. Pour the marinade over the chicken and beef and rub the marinade all over the meat. Give your hands a good wash, and then cover the dishes with cling film and let them marinate in the fridge for 4 to 6 hours.
3. For the pico de gallo: Chop the tomatoes, jalapenos and onion into a very small dice. (Leave the seeds in your jalapenos for a hotter pico. Adjust the amount of jalapenos to your preferred temperature.) Next, chop up a nice-sized bunch of coriander. Just remove and discard the long leafless stems before chopping. No need to remove the leaves from the stems completely. Place all of these ingredients together in a bowl and give it a good stir. Squeeze the juice of half a lime into the bowl. Add salt to taste and stir again.
4. For the fajita vegetables: Throw the onions and bell peppers into a bowl and toss with the olive oil and some salt and pepper.
5. When ready to cook, preheat the grill to high heat.
6. Cook the chicken on both sides until completely cooked through (or to an internal temperature of 75°C), about 4 minutes per side. Remove it to a platter to rest for 5 to 10 minutes.
7. Grill the beef on both sides until completely cooked through, about 5 minutes in total. Remove it to a platter to rest for 5 to 10 minutes.
8. Tip the fajita vegetables into a grill basket and grill until cooked, tossing occasionally, about 10 minutes.
9. To put it all together: Pile the veggies on a platter. Slice the chicken and beef.
10. For the extras: Wrap the tortillas in foil and warm through on the grill. Serve the chicken, beef and veggies with the warm tortillas, refried beans, grated cheese, sour cream, lime wedges and pico de gallo.