That only addresses part if it. The OP still needs to go in and prevent his items being shown on overseas sites. If his listing shows as posting to worldwide, then blocking addresses he doesn't post to, isn't going to stop anyone.
OP, tick all the boxes next to the items on your selling page. You can tick them in bulk by going to the bottom of the listings and ticking the box that isn't next to an item. Then select the edit button. On the next screen, tick the box at the top of the listings shown to tick all the boxes at once. Then click on "edit fields", and then "postage (international)". Change the dropdown to no international postage, and then save and close. Then click on the big blue submit changes box, then the confirm and submit button.
To be doubly sure they can't buy, click on the Account tab, then site preferences. Scroll down to postage preferences, then click on the postage preferences highlighted link. Scroll down to exclude postage locations, and click edit on the right hand side. On the next screen, tick all the boxes under the international heading, then apply to current listings, and then save.
When you want to sell internationally again, untick the boxes of the countries you wish to post to again in the postage preferences. If you are offering flat rate postage, you can set that back up in the bulk edit like above. If you are offering calculated postage (where depending on where you live, depends what it costs), you need to set them up manually by editing each listing individually. There is the option of calculated shipping in the bulk edit, but for some reason after you save it, it doesn't show a postage cost for the buyer.
I hope I've explained this OK!
