I don't know if this will help anyone here, but I have just performed the dreaded move images to the file system (if only we knew this when we started). Anyway, when I first did it, I thought that the images were still in the DB and as others have done, deleted them only to find they were no longer in the shop.
My point is this, when I checked carefully, it only appears that the images are still in the DB, when in fact they are now just references to the images now on the server. The DB no longer has the massive Blob data just the new file locations, so should be smaller.
Like others, I was worried about doing this operation with the fear of it failing and having to reload tons of photos, but followed the help here and it was fine.