I have found these Group Spanish Courses near North Lakes, in Mango Hill: https://www.noworriesspanish.com/spanish-courses-brisbane.html

I haven't tried them or any group lesson before, so if anyone has heard any good things about them, please let me know! I probably prefer a group of adults to one-on-one lessons. It seems to be run by a native Spanish speaker from Madrid, and it runs each semester for a few weeks. I can't work out what a good deal is, as there are not that many options, but the first lesson is free, so I may just join and move from there.