Complex sentence: In 1999, Hawker Britton outgrew its The Rocks office, relocating to a heritage post office building in Millers Point, it now has over 6 Australian offices, an office in Wellington, New Zealand and 3 international offices in Washington, D.C., London and Shanghai.
Split into simpler sentences: In 1999, Hawker Britton outgrew its The Rocks office, relocating to a heritage post office building in Millers Point. It now has at least six Australian offices; an office in Wellington; another in New Zealand; and three international offices in Washington, D.C., London and Shanghai.