The visa policy of each country is based on reciprocity; therefore citizens of countries that insist upon entry visas for Latin American citizens will need entry visas.
British citizens currently do not require visas for visits to any South American country, however other nationalities may differ, most notably Americans, Canadians and Australians. Check with the Consulate in your country.
Passports must be valid for at least six months from the date of entry. Take good care of the “ENTRY/EXIT CARD”, which is given to you in some countries and must be completed upon entering. The document may have to be checked and stamped by the Federal Police on entering and leaving the country.