Place the couscous in a bowl, squeeze over the lemon and add the zest, olive oil and seasoning. Pour over the boiling water, stir, then cover with cling film or a plate and set aside to soak for 5 minutes. Fluff with a fork and check the seasoning.
Fold the cucumber, tomato, herbs and chicken through the couscous. Divide generously between 4 wraps, drizzle with the yoghurt, fold in the ends and roll up, securing with a cocktail stick.