The national archives of Argentina and its branches arde open to the public. Microfilm copies of some records at the national Archiv are avilable at the Mormon Family History Library(othermajor archives and librafries and branches of the national archives.
The address of the national Archives of Argebntina is (e-mail) archiviomininterior.gov.ar
Now there is a commercial genealogy company that may help you for a fee (in english) www.familias-argentinas/com.ar and select british flag for english. Petertimber