In a small bowl, combine Worcestershire sauce, soy sauce, honey, vinegar, lemon juice, mustard, salt, celery seed, pepper, and garlic. Place pork loin roast in a large plastic resealable bag and pour marinade over pork loin. Seal and marinate in refrigerator for at least 4 hours (preferably overnight).
Preheat oven to 325 degrees F.
Remove roast from bag, place in a roasting pan, and discard marinade. Roast pork loin at 325 degrees F for 2 to 2 1/2 hours, or until an internal temperature registers 160 to 170 degrees F on an instant-read thermometer. Serve with BBQ sauce.