It appears that the user command framework searches the source folders under options/configure/UserCommands AND all of the subfolders of said source folders.
Is this a bug or a feature?
This has the interesting side effect that if your user command has additional resources located in a folder that is a sibling of the .dyalog file, and one of those resources happens to be a {usercommand}.dyalog file then this will get loaded or attempted to load up too. I got around this by renaming the .dyalog resource to .txt.
On the plus side, it means that when distributing a user command that requires additional resources, the .dyalog file can be in the same folder as those resources, and we don't need a special entry in the configuration settings; we can drop a single folder (rather and file and an associated folder) containing a .dyalog file anywhere underneath it, into say the c:\users\paul\documents\MyUCMDs folder, and that's it, that's all we have to do.