What countries use BST?

Could you please clarify which BST you are referring to? If you mean British Summer Time (BST), it's a time zone observed in the United Kingdom, parts of Europe, and some other territories during the summer months. Specifically, BST is used in the United Kingdom, Ireland, Iceland, and some parts of Portugal, Spain, France, Belgium, the Netherlands, Germany, and Norway. It's important to note that BST is not a currency or a financial instrument, but rather a time zone adjustment used to align with daylight saving time practices.