Ok, fair enough.
I'd be careful with how you phrase it.
Something like "the Australian accent shows little regional variation relative to other countries such as England" sounds better
I think it's generally accepted in linguistics circles that Australian English is homogenous, and you wouldn't need to compare it to e.g. England or America. Phonologically, you can often tell someone is from the country by their broad accent, but it would be really hard to decide which city/state they are from. As Macmillan says, the homogeneity of AE grew out of a melting pot effect -- all the accents merged when Australia was settled, and it settled fairly quickly.
In the essay, you could also talk about how AE is losing some unique characteristics to American English. e.g. lexical items such as "bling" and "eye candy" have been introduced, and some American slang terms replace the once widely used "bonza/bonzer" etc. Also, many newspapers use American morphemes such as -or instead of -our (however, this is also for economy of characters).
The varieties of AE are also unique; Broad, Cultivated, and General each have unique features, as well as Aboriginal English, etc.