Combine the Smoked Paprika and Classic Barbecue together in a small bowl. Season with Salt, then rub all over the pork.
Place the onions and Bay Leaves into the base of a slow cooker set on high. Pour over the cola and sit the pork shoulder on top, cover and allow to cook for 4 4 ½ hours depending on the size of the joint. The pork should easily come apart when pressed with a fork.
Carefully remove the pork from the slow cooker and transfer to a large dish. Strain the liquid into a jug. Allow to stand for a few minutes for the excess fat to rise to the top then skim off. Place a shallow pan over a high heat and pour in the liquid, along with the tomato ketchup, red wine vinegar and Worcestershire sauce. Simmer for around 10 minutes stirring, until the sauce thickens and begins to turn sticky.
Shred the pork with a fork and spoon and drizzle over half of the sauce, toss the meat to coat. Serve in brioche rolls drizzled with the remaining sauce.