Cook bacon slices in a deep skillet over medium high heat till they are evenly brown. Crumble and keep aside. Toss broccoli and chopped onions and raisins. Prepare a blend of white sugar, vinegar and mayonnaise. Pour over the broccoli pieces and toss to coat evenly. Refrigerate for a few hours. Sprinkle sunflower seeds, cheddar cheese and crumbled bacon before serving.