Because I was very busy, I didn't have time to go to the store. Because I had plenty of food in my house, I didn't need to go to the store.

--I didn't have my travel alarm clock, but I didn't need it, because I can use my cell phone as an alarm clock. --I thought that I couldn't make the recipe, because I didn't have any maple syrup. Then I decided that I didn't need maple syrup, because I have brown sugar, and that's close enough. There IS a usage in which "have" and "heed" can mean the same thing: "have to" and "need to." There really isn't any difference in meaning and I can't say how I decide which to use. (I speak U.S. English). --I didn't have to pay anything, because my friend said I could be his guest. --I didn't need to pay anything, because my friend said I could be his guest.