If you really want to be a cockney, you need to write in back slang, or rhyming slang.
Ti teg uoy od.
I doubt you'll even understand what i'm saying if I ever done that
well, it may hurt some natives around here especially when doing the suggestion of australian accent, I heard they don't want them to sound really bad or sucks trying on their language. Though this may only be a joke but there would be a lot of whining after that. 
fuck it - ill give you merits just for trying, if the accent is that bad then It'll be worth it. Come on man - its all a bit of a bubble.