Hello Demon,
Here in Spain we have a lot of species of Olive trees. Yo should decide which one to choose considering climate, depending if your area is a cold one in winter (freezing in winter?). There are many species like Picual, Picudo,Empeltre, Hojiblanca, Cornicabra, Lechín de Sevilla, Manzanilla Sevillana, Manzanilla Cacereña, Verdial de Badajoz... (sorry, can´t translate it in English). Anyway the two more resistant to cold conditions are Picual and Picudo.
Hope this may help you,
Salvatore