Ah! Thank you, I was unsure if the C64C hit Australian shores. That definitely helps, I'll tweak my post accordingly.

For what it's worth, here's one of the Australian C64 commercials of the era, clearly featuring the C64C. The original C64 breadbins were also very common in Australia:

https://www.youtube.com/watch?v=OALMEpfWswM

The guy in that ad (John Laws) was a very famous talkback radio personality at the time - nowadays he'd probably be likened to a Fox News personality like Tucker Carlson. He was featured on the packaging art for the Australian C64 Family Pack, as seen near the end of the commercial. He was known to begin every episode of his radio show with the phrase "Hello World".

Note that Commodore bundled the Family Pack with a random book (mostly pictures?) about Australia. For some inexplicable reason there are an awful lot of secondhand copies of that Presenting Australia book available on eBay to this day.

Never seen one of these Slimline C64 Replacement Cases before. Intriguing!

If it has the heavy power-supply, consider replacing or repairing it. It fails over time by increasing the 5V rail until some chip or other fries in the C64.

Ah cool, I’ve replaced so many of these in the past!! If I recall, RetroKit and a few other stores sell more reliable modern PSUs.

Do any of your cassettes from that era still load?

If they don't, you can just record them again from the internet.