In trying to set up FTP access on another Mac with OS X server, I realised that I missed a point in my previous short tutorial:

Before doing anything else, go into Workgroup Manager, and click on the ‘Sharing’ button at the top. There should be 2 tabs underneath - ‘Share Points’ and ‘All’. If the parent of the directory you want to allow access to is in the list, all good - you don‘t need to do anything else. If not, then click ’All‘, find the parent of the directory you want to share and click on it. Then in the right hand pane, under ’General‘, enable ’Share this item and its contents'.

Then carry on with the tutorial as before.

Hope this helps someone. SteamSHIFT out.