As has been said, the only reason that the Brit version of Top Gear works is because of Clarkson, Hammond and May. Top Gear has been around since 1978, but was canceled in 2001 after Clarkson left the show to do other work in 1998 and the ratings slid, thus seeing most of those working on the show at the time take up an offer from Channel Five to continue the original format under the title "5th Gear". If you want to see why Top Gear never made it to Australian tv before a couple of years ago, catch an episode of 5th Gear. Yawn.
The show was uncanceled for 2002 when Clarkson and Hammond agreed to join the only remaining cast member, James May, on a new format show.
I expect the Australian version of Top Gear to be full of crap wannabe Australian "characters" giving us crappy reviews of the latest Dunnydores and Farkons. Australia is, sadly, devoid of anyone with charisma. The end.