TO treasure-hearts   In regards to bulk purchase of registerd post lables, do you still need to go into the post office for them to stamp the reciept thingy or can you simpply drop your mail in the post box?

I'm no treasure . . . but the 'receipt thingy' does need to be stamped by the post office.  The receipt has the registration number and the address that the registered item has been posted to . . . . . which is proof that you sent the item to the address that appears on the PayPal payment notification.  PayPal would not deem a registration number alone as proof of posting to the buyer.