So using the links from Andy_Mac, and Pharnos' instructions on LegacyGT.com, I got that ADB and Fastboot installed on my PC, and sorted out the off-mode-charge setting.
Pharnos, mate you're a bloody legend for working that out and posting it up, and Andy_Mac, you're a legend too for posting up the links to it. Thanks heaps guys, that made my night tonight 😊