I've learned how use Amazon during the past couple of months or so, but I can't get to grips with free delivery, yesterday I ordered about £500 worth of kit for our camera and there are 4 items, the most expensive item I've got free delivery but the other three items that amount to less than £150 I've been charged a total about £14 delivery and they are a lens hood a filter and a fluid head, so not large or heavy package, but checking their site it should all be free delivery and the procedure is to me very complicated. Can someone help please?