Ok, so my stop-gap solution was as follows -
Installed Alley (and exporter plugin) on a friend's computer (who had Premiere installed).
Then went to:
And copied the "Resolume DXV" Folder, to my computer under:
C:\Program Files\Adobe\Adobe Media Encoder CC 2018\Plug-ins\Common
Restarted Media Encoder and success!
Unfortunately as Zoltan said, it appears when you just install Media Encoder it doesn't create the Common directory that the Resolume Codec installer is looking for, so assumes that you do not have any adobe products installed to load the plugin. Would be good if this could be updated in the Alley and Resolume installers to also install to the Media Encoder directory, although this is more of an Adobe flaw than Resolume's issue.
Lighting | Audiovisual | Design