Double-check that you have blocked buyers with a primary address in a location you don't post to - I have no exclusions at all and just have my postage preference set up to post to Aus only, with this block in place no one outside of Aus can buy (blocked bidder activity has always shown attempts - some sellers have said this doesn't work for them and they've had to set up an exclusion list like you have, but I don't know why). 

https://www.ebay.com.au/bmgt/buyerrequirements