Slit the frankfurters almost through lengthwise. Mix the pickle relish and prepared mustard together. Cut the cheddar cheese into 12 4 1/2 by 1/2-inch strips. Put one strip of cheddar cheese and about 2 tsps of the relish mixture into each frankfurter and set aside. Panbroil the bacon until partially cooked and still limp and drain. Starting at one end, securing the bacon with a wooden pick, wrap each frankfurter and secure the other end with a wooden pick also. Set the oven temperature to broil and arrange the bacon wrapped frankfurters on the broiler rack with the tops 3-inches below the heat source and broil until the bacon in cooked, turning once. Serve hot in the buns.