Late night munchies can be a real problem for a lot of dieters! My first suggestion is to get rid of the M&M's
If you have trigger foods available to you, you are more likely to give in. Just don't even buy them. If they aren't there, you can't eat them.
Keep diet-friendly foods on hand that will help your munchies, but probably not be easy to overeat. Carrot sticks with nonfat ranch dip are good. Flavored mini rice cakes are also good, especially on Weight Watchers. A glass of V-8 juice is suprisingly filling. Using your Weight Watcher guides, make a list of acceptable snacks, and work them into your daily menu. Plan your munchies
I'd love to hear any other suggestions for this topic!