The difference is that when aircraft leave Gatwick they're heading to the four points of the compass. When aircraft leave Perth they're generally heading in one. I suspect that it's not runway capacity that is the issue but airspace capacity.
Yeah I don't doubt that Perth ATC and airport have its problems, but it's about owning the problem and providing a solution. Australia needs to solve it's aviation infrastructure problems and it has to come from people at the top. If he needs new rules he should get onto it. If he needs bigger airports he needs to sort it out. That what a CEO does. If you get hamstrung by the government or private airport owners you need to put the heat on them.
I can't think of to many industry leaders who would go onto the ABC and say that his customers need to change their entire business setup (which is what a roster rewrite would mean) because we can't be bother to fix our systems or attempt to do anything about it.
Another example of why we need an Australian Aviation Lobby or political party.