In a large, self-sealing bag, combine honey and Worcestershire sauce. Add chicken and place bag in a shallow dish in the refrigerator. Chill 2 to 4 hours, turning bag occasionally. Remove chicken and discard marinade.
Grill chicken over medium heat for 12 to 15 minutes, until juices run clear and chicken is no longer pink inside. Remove from grill, cool and chop.
In a medium bowl, whisk together the remaining honey, mustard, vinegar, lemon zest, lemon pepper, poppy seeds and garlic powder. Add chicken, grapes and cashews and toss until evenly coated. Cover and chill until serving.