Blend marinade ingredients together. Transfer half to a ceramic bowl and add Chicken and stir to coat.
Cover and place in fridge for several hours or overnight.
Combine marinade and mayo and adjust seasonings.
Place vinegar, sugar and salt into a bowl and whisk to blend until sugar dissolves. Add cucumber and place in fridge for at least 20 mins.
Preheat Barbecue on med-high. Remove Chicken from the marinade and place on BBQ. Turn chicken and cook until lightly charred or cooked through.
Meanwhile lightly oil the cut sides of the buns and toast on BBQ, cut side down for 2 mins or until lightly toasted.
Spread the Peri Peri mayonnaise over the bun bases. Top with chicken pieces, then cucumber, onion and coriander and lettuce to serve.