Passport validity: your passport should be valid for the entire duration of your stay. No additional period of validity beyond this is required.
Visas: At the time of writing, UK citizens don’t need a visa to enter Argentina as a tourist unless you’re travelling on an Emergency Travel Document. On presentation of a valid British passport you will be granted a 90-day stay in the country. If you are travelling to Argentina for any other purpose, contact the Embassy of the Argentine Republic in London. Always check with the Argentinian embassy in your country before travelling.
Proof of onward travel: you may need to provide proof of onward travel in the form of a return ticket. You should make all flight reservations before departing for Argentina. Airlines have sometimes refused to board passengers travelling to Argentina without proof of onward travel. If you are transiting through the US, you may need a visa if you decide to leave the airport as a stop-over.
Health: Buenos Aires is generally a safe place to travel. For yellow fever (as we won’t be travelling to the north of the country), under International Health Regulations (2005), there are no vaccination requirements for any traveller visiting this country. We recommend you to contact your GP for the latest list of recommended vaccines, or take a look at the pages below:
http://www.nathnac.org/ds/c_pages/country_page_AR.htm
http://www.fco.gov.uk/en/travel-and-living-abroad/travel-advice-by-country/south-america/argentina
http://www.lonelyplanet.com/argentina/practical-information/health