My own instinct would be to set up a parallel website. e.g. if your current site is ck1value.com, register ck1value.com.au as a separate domain name. It's not expensive:
https://www.netregistry.com.au/domain-names/domain-pricing/
You'd have to pay for hosting that second site but, again, it shouldn't cost much. (Your existing provider might be able to offer you a discount for hosting both sites).
You could then set up your original website to detect traffic from Australian IP addresses, so that visitors from down under see a message such as this one:
"It looks like you're in Australia. To see our Australian website, with prices in AUD, please click HERE. (If you'd prefer to continue viewing our UK site though please click HERE)"
You could also add something (on your original site) to the shipping page, roughly along these lines:
"Please note that we don't ship products purchased from
this site to Australia. However some of our products are available on our Australian website. Please click HERE to visit it"