when you sell an item and use sellers standard rate. you need to be aware that if the buyer pays through paypal putting i obtain proof of posting and not responsible for items lost is worthless.
the royal mail states that for all claims it is the senders responsabillity to claim for lost items, as only they have all the information needed to claim.
PROOF OF POSTING IS NOT PROOF OF DELIVERY and as such does not protect you from item not recieved claims.
if the buyer has paid you by paypal and says that they have not recieved the item. and you cannot provide online tracking information for the item then paypal will refund their money. as per their terms
cover yourselves by sending by recorded del for items under £28 in value or special for items of greater value as there are claim limits