I'm not familiar with Australian law and its definitions, but I'll try to sum up each book for you so you can come to your own conclusions:
Renai Sample has a flat-chested girl. The main character (MC) questions her age at one point and refers to himself as a lolicon (both in a comical fashion). According to the story, all the characters seem to be in university, and she's actually older than him.
PuniKano has a petite (demon) girl. MC refers to her as a "little girl" and "brat," but he himself seems to be in his late 20s or early 30s.
Peachy-Butt Girls has several flat-chested girls.
Welcome to Tokoharu Apartments has two flat-chested girls, but they're both in university. There's also a flashback to what seems to be one of the characters when she was in high school.
Hanafuda has a chapter with
clearly underage characters, and this is probably the only book so far where this is the case. Note that this one currently only has a digital pre-order available.
Melty Gaze has a one-panel flashback with the main characters trying to have sex. Nothing explicit is shown, and the story implies that they didn't go further than some petting.
Alluring Woman and
Porno Switch shouldn't have anything worth questioning.
The last time I looked at some of the other books was when I did the translation—which was months ago in some cases—so I don't have them all super fresh in mind, but none of them will be available for quite a while anyway. That being said, for NaPaTa's
Love-Ridden, I don't think there's anything besides some flat-chested girls.
In general, most books have the same setting as the majority of anime and manga—i.e., high school—but with the exception of Hanafuda, I'm pretty sure none of them explicitly state that a character is underage. I wouldn't classify any of those loli.
Our books also have the following disclaimer at the end of them:
All characters depicted in sexual or erotic acts in this publication are the age of majority or older, not withstanding suggestions otherwise presented within the work. All characters appearing in this work are fictitious. Any resemblance to real persons, living or dead, is purely coincidental.
If you want me to have a closer look at any book you're interested in, feel free to PM me or reply here.