Just ran "Cleaner" on Ccleaner (first time) less than 24 hours ago to free up space. It freed up over 10 GB to give me 35.5 GB free
space. Now less than 24 hours later the free space has shrunk to 33.9 GB free space, any ideas as to why? No new restore point has been
created if that helps.
use WizTree from here; https://antibody-software.com/web/software/software/wiztree-finds-the-files-and-folders-using-the-most-disk-space-on-your-hard-drive/ and find out where the space is going.
You didn't state what your operating system was. Although you state it isn't System Restore related -- however see if this is what's possibly consuming hdd space:
https://forum.piriform.com/topic/52500-windows-module-installer/?do=findComment&comment=299146