I just want to point out ... You really shouldn't charge your buyers for Signature on Delivery or Registered Post.   It's better to put that cost into your start or BIN price because a lot of buyers don't like the idea of paying for your seller protection.   Just some food for thought.

Only people that think that's all reg. / SOD is for. Considering registered post was around 100+ years before eBay and PayPal, some people believe it has a different purpose, like protecting the value of the item should anything happen to it in transit. 

Registered / insured post also means the seller has a legal obligation to seek any compensation payable and pass it on to the buyer, so if the seller has protection without a registered / insured service being used, the buyer may be lucky enough to get a discretionary payment from somewhere, but it's by no means guaranteed.