I bought a chain from JE James once that was posted recorded delivery, and the postman just put it through the letter box without getting a signature for it.
When I went down to the delivery office, they looked on the computer but couldn't even tell me whether it left the post office where I posted it. They told me that recorded letters that aren't delivered are returned to sender, but I doubt that as the recorded delivery stickers don't have the senders name and post code written on them any more. When I posted a second letter by registered post I asked what happens if the recipient refuses it, and he just looked blank and said "why would they do that?". He wrote my name & address on the back of the envelope to humour me, but unless there's an organised system for returns I can't see that making any difference.