Yes, everyone needs a visa to go to Australia. Most British citizens if they are just going for a holiday get an electronic visa - either a free e-visa from the Department of Immigration and Citizenship or, for a small handling charge, you can get one from your travel agent. There is more information about this here.

If you want a longer stay or are looking for work, you have to get different types of visa. There is a good overview here. For instance, if you have a job arranged in Australia you will need your employer to sponsor you; if you are a skilled worker or professional you may be able to look for work, but you have to fill in a special appliation first.

If you don't find all the answers you need through the above links, you can contact the Immigration Department directly through this page. Hope this helps.