I've just bought some for my imminent whelping and got it from hyperdrug, they sent it by normal 1st class post. It came the next morning and I popped it straight in the fridge. I've always kept them in the fridge as it's always said it needs to be kept cool on the box. I pretty much always end up throwing it away, as they don't have a long shelf life even unopened, but I figure better safe than sorry so always buy one in-case there's a problem.
Actually if I don't need it I'll pop it on here and send to someone for the cost of postage as otherwise it's a waste as wont be having another litter until next Summer; I used to sell chocolate to ex pats and have loads of cold packs so can post it with one of them.