Permissions Issue Radarr/Sonarr/Bazarr/Cockpit/SABnzbd etc

[OptimalGrammar]

I've been struggling to get this right for a couple of weeks now & it's actually become a roadblock now.
I'm trying to get read & write access to host storage within the LXC's, & after attempting to follow various guides online, I'm stumped.
On the host, I have the group nas_shares:x:110000: along with user nas:x:101000:110000::/home/nas:/bin/bash.
On each LXC, I have the group nas_shares:x:10000: and user nas:x:1000:10000::/home/nas:/bin/bash
I've done the chmod & chown commands on the mountpoint, so it's owned by nas:nas_shares & has 775 set. Despite this, I have no write permissions in any of the services mentioned in the title. My suspicions are that each of the services are running as root & are not getting use of the permissions I've set up.
Question is, can I make each of the services run as the nas user & get them to have read & write access?
I did try the script bash -c "$(wget -qLO - https://github.com/Sonarr/Sonarr/raw/develop/distribution/debian/install.sh)" from #1316 & set the user & group, but that hasn't made a difference, & there doesn't seem to be an equivalent script for the other services.
Could anybody point me in the right direction?