Preheat an overhead grill to hot.
Season the pork chops with BBQ spice rub, salt, black pepper, and a drizzle of oil.
Place the chops under the grill and cook for 3-4 minutes, then brush with BBQ sauce and cook for another 3-4 minutes.
Turn the chops over, brush with BBQ sauce and return to the grill. Cook for 3-4 minutes and brush with more BBQ sauce, then grill for another 3-4 minutes. Repeat until the pork chops are cooked through.
Remove from the heat, brush with a little extra BBQ sauce, and allow to rest for five minutes.
Serve with watercress and extra bbq sauce.