I've never had Nandos, but this is what I found and I hope it's close to the real thing? FYI, I cooked mine with the deflectors in the mid position at 400F and it turned out great. I also used olive oil, not vegetable oil.
Peri Peri Chicken
For The Marinade:
1/2 cup vegetable oil
1/3 cup BBQ sauce
3 tablespoons Worcestershire sauce
2 tablespoons minced garlic
1 tablespoon onion powder
2 teaspoons fresh squeezed lemon juice (optional)
2-4 teaspoons sriracha*
1 teaspoon yellow mustard
2 teaspoons salt
Cracked black pepper , to taste (optional)
3-4 pounds (or 1 1/2kg to 2kg) whole chicken (Butterflied is preferred)
Salt and pepper to season
Mix all of the marinade ingredients (except for the Sriracha) together until well combined. Mix in 2-4 teaspoons of Sriracha, taste test, and work up from there until reaching your desired level of heat (or leave it out all together if you don't want any spice at all).
Using 3/4 of the marinade, coat the chicken evenly on the outside, as well as under the skin where possible (the breast especially), until fully coated in sauce. Cover with plastic wrap and refrigerate over night if time allows. (I recommend a minimum marinade time of two hours for this chicken. The longer you leave it, the better the flavours.)
FOR THE BBQ:
Place chicken on well-greased grill over medium heat, skin-side down, for 10-12 minutes, until the skin begins to have a nice char on it. Add 2 more tablespoons of vegetable oil to the remaining marinade. Flip and baste with a small amount of sauce (not too much or it will burn on your grill plates). Close barbecue lid and cook for 40-45 minutes, flipping once or twice while cooking, until chicken is completely cooked through and juices run clear.
Follow corn foil instructions above. Place corn foil packets on the grill halfway through chicken cook time (after 30 minutes), turning the corn every 5 minutes or so to ensure an even char.