Morning mike, from memory if you "Revise " your item and go about 3/4 down the opening page (near the postal bit) you should find the bit about international bids and you will have to alter it to allow international bidders.
Also you maybe best (subject to wot you are selling) to put a note to these "International bidders" outlinning that YOU ARE NOT LIABLE for any duty that their purchase may attract at their local customs office. You may get asked to be a little conservative with the items description and value. They the buyer will/may end up paying duty on wot you are selling and if so an undervalue on your part means they pay less tax.
Its your decision but if customs decide to check (and they do) you will be in hot water too.
Hope that helps.
Regards Paul