Not that I can't override everything it's doing in my custom css file, but on a custom theme this doesn't really help anything on my layout so I'd rather just stop it from being loaded.  What's the best way to get rid of since it's being called from core files?

Accepted answer

As per https://docs.backdropcms.org/documentation/creating-sub-themes, to override existing CSS you just specify a stylesheet with the same name in your .info file and then have an empty file in your theme.

Comments

Thanks BW, that does the trick (thought it would be a theme-settings thing, but so long as it works I'm happy.)