If they're not detected by the BIOS it's a serious problem. Coupled with the clicking it sounds like typical hard drive failure.
You are not allowed to mention competitors on this forum, I suggest you edit them out of your post ASAP.
You have your statutory rights regarding these matters, there's no reason why the retailer should not replace an item that was faulty on receipt, when you send them back they'll see they're faulty and replace them for you, or send them off to Samsung for repair. As I said, depending on the retailer, they may just send new ones, OcUK often do this with faulty items I've noticed. As for other retailers, I can't say, but there's certainly no need to buy insurance against faulty items whilst they're in warranty.