Although all the advice is low fat this and hi-carb that, you do need some fat and some protien in your diet to stop you feeling hungry and to help your body repair itself.
How about an egg on your toast in the monring, a handful of nuts and raisins with your grapes mid-morning, and maybe the aforementioned malt loaf instead of your cereal bar (they're not all that nutritious generally). If you can do a baked potato with a reasonably healthy filling for lunch, that might help too.
Depends how many miles you are running, but you sound like you aren't eating enough anyway, so that'll be why you feel like snacking so often.