Calendar application doesn't search my contacts addresses correctly

When adding a new calendar item on my iPhone, I touch on the Location field to display the Location search. I want to select a contacts address, but the search doesn't display all my contacts addresses. I have addresses stored for most of my contacts, however the Calendar app wont bring them up.

For example, when I search for my surname, it should bring up all my family members under a section "Contacts" however some of my family doesn't appear, but some do.

Under the "Locations" section, it's also displaying a number of locations in the USA which is completely useless and irrelevant as I'm in Australia.

Any ideas why it doesn't work?

Cheers,

Tris.