I have orderd an item and have accidentally continued with only my postcode, how can I change the delivery address to show both my postcode and rd name/ number
You should contact the seller asap and let them know. The odds are they will contact you anyway as your address is inadequate. They will probably have to cancel/refund the transaction and relist so you can buy again with all the correct details on your account.
I contacted the seller and he has sent it from Poland to uk warehouse already, he said he can ask them if it can be operated to add a note onto the package. What do you think?