England decided to colonise Australia for the following reasons: 1. To expand the British empire, and prevent the French from gaining a foothold in the Australian continent or in that part of the Pacific.2. The continent had natural resources which England wanted.he British decided to colonis … e Australia for several  reasons:    1. To expand the British empire, and prevent the French from  gaining a foothold in the Australian continent or in the southwest  Pacific.    2.