Sydney I've only driven around a couple of times and Perth not at all. My impression is based on all other state capitals and country driving. A high percentage of the time, if you put the indicator on to show an intended lane change the vehicle behind will accelerate to close the gap and keep you out. My (limited) experience in UK is that the majority of drivers back off and assist the change.

Don't want to take the thread topic away from GPS though and start an interstate civil war. :)