WordPress: cleaning media library

I’m giving my website a clearout whilst I redesign it, and thought I’d delete a bunch of old images from the media library (about 50 or so).

I thought this would free up a lot of space, but now I see they are all still in my /uploads folder. I imagine this is due to me having multiple sizes of the same images.

Now these images are no longer recognised in my media library, is there any way to scan what is in the folder and remove those that aren’t linked to any posts?