So I moved the rclone mount and chucked it in the /media/data directory as firstly that's a far more logical place to have it and secondly because that is the same location I have my backups folder, which I can share via Samba without issues....
It still doesn't work 
The only obvious difference I can see is that the backup folder is owned by root and my mount is owned by my user. I'm reluctant to change my mount user and group to root as I feel like that could be opening a can of worms, but I can't think what else to do now.
Does anyone have an inspired suggestion they can throw my way? 