var prompted = false;
function chkCountry(elem)
{
    if(elem.options[elem.selectedIndex].value!='GB' && elem.options[elem.selectedIndex].value!='none' && !prompted)
    {
         var result = confirm('Please note an additional charge towards carriage will be incurred on orders to be shipped outside of the UK. Consent for the additional payment will be required before your order can be despatched. If you choose to proceed you will shortly be contacted by a member of our team');
         if(!result)
         {
            // reset to GB
            elem.selectedIndex=0;
         }
         prompted = true;
    }
}