if you tell them that you KNOW they have it - as royal mail have informed you of this, they HAVE to give it to you...it is theft otherwise - you have PROOF they have it, so its hardly likely they will just say no...!
you cannot expect them to come to you... if i take a parcel in for a neighbour - they collect it from me - i do not deliver...
you do not have a leg to stand on... you cannot bandy rouud all this threatening outraged tone, as though you have been wronged, when EVERYONE EXCEPT you has done exactly as expected...
why should the seller lose cash and goods because you wont walk 2 doors down?
i would laugh in your face i am afraid if you demanded a refund from me when the goods are with your neighbour and you knew it
in futurem you can request that the PO dont leave your post anywhere...but if its a courier you cant really control it...