There are a number of British Embassies and High commissions around the world. From British Embassies in South America to Asia, Africa and East Asia. If you need consular assistance then you can contact them or renew your British passport online. Search this website for more details on this.
Below you will find the most commonly used British Embassies in South America. See each page for the contact details of the Embassy and always ensure that you have all your needed documents as well as ensuing that the Embassy is open on the day you pay them a visit. British visa applications will need documentation and you should speak to an immigration lawyer about this. Also note that emergency travel documents normally need a police report from the country where you lost your passport in.