In addition to the advice that has already been given, if you do not want to receive bids from buyers in some - or all - overseas destinations then tighten up your Selling Preferences so that bidders living in coutries you are not prepared to post to cannot successfully place a bid in the first place.
In order to set this up go back to your My eBay page and click on the Account tab. Look at the Account Preferences section on the right hand side of the page at the top of the screen and click on Site Preferences. A new page entitled "Site Preferences" will load up. Scroll down to the section entitled "Postage And Packing Preferences" and click on the link in that section.
Once you have clicked on the link a new page entitled "Manage Postage Settings" will load up. Scroll right down to the bottom of the page and look at the second to last sentence on the page. There are three columns. The left column says "Exclude Postage Locations", the middle column says "Domestic", with "International" directly below it, and the last column on the right of the screen is a link that says "Edit." Click on that link and a new page entitled "Exclude Postage Locations" will appear on the screen.
When the "Exclude Postage Locations" page loads up you'll see two sections to the page. The top half is entitled "Domestic", which is to block regions within the British Isles, whereas the bottom half of the page is entitled "International" and will enable you to block any overseas countries - or even whole continents - that you wish to list as countries you do not post to. If you want to block the entire continent for any region listed just tick the main box and buyers from every single country in that region will automatically be blocked from purchasing anything from you. If, on the other hand, you want to block some, but not all, countries from various regions on the page click on the "Show All Countries" link to bring up a drop-down menu of every country that comes under that area. Tick the boxes next to the countries that you wish to block and leave the boxes unticked of any countries that you don't mind posting to. Once you're finished click on the "Hide All Countries" link to close the list. Repeat the same procedure to block certain countries within the other regions shown on that page, or if you want to block the lot just click on the main box next to the name of the region in question. That way you won't have to block each country individually.
Once you've finished blocking all of the overseas destinations that you do not wish to post to scroll right down to the bottom of the page. Tick the box next to the option that says "Also Apply To Current Listings", then click on the blue Save button to confirm the changes. Once you have done that buyers living in any countries and/or regions that you have blocked will be unable to place bids on your auctions or purchase anything you've listed using the Buy It Now format. If you do that then you won't have to worry about unwanted international bidders purchasing your items and leaving you with the hassle of either having to cancel the transaction or posting the item to an overseas destination that you weren't really willing to post to in the first place.
