You should be able to send PAYMENT DETAILS in other words an invoice, but edit the postal details.
Looking at one of your listings you ship to Australia so should be simple enough.
This is the trouble when you do not quote overseas postage, unless a country is Blocked anyone can bid or buy, but cannot pay. You should either block countries you do not post to or provide an overseas shipping cost on your listings. There are many Countries with poor postal services, and it is far better to block than have to cancel sales which.
Also of course you will need to complete a Customs Declaration, and find a tariff code.
https://www.trade-tariff.service.gov.uk/a-z-index/m