Hi Arran.
Since this script was written by me on 'Debian', building on preliminary stuff from 'yahvuu', I have an interest.
There many autosaves, for example a more recent one is a 'Perl' script also at the registry, did not try it!
The two preceding examples of this plug-in are on 'Windows', on the Linux distribution Fedora 20 it looks like this in my GIMP-2.8.14:
In the following brief explanation: number refer to label on the red circle
(1) There is two plug-ins in the version 0.3 : the main one is 'Auto save' and it should be launched with an open image.
The other 'NoUI auto save' don't need an image and need minimal user intervention.
The menu path: it's where I put the 'Plugins-Python' which are not part of the GIMP distribution.
(2) This is the window of 'Auto save'. The frames 'Directory', 'Files' and 'Time' make the config area.
The minty green background line indicates a running instance of 'NoUI auto save';
usually if you want to use 'NoUI auto save', you run 'Auto save' before to set 'LastStop config' which is use by 'NoUI auto save'.
When you press 'Start' the button label change to 'Stop', if you search for 'Stop'!
(3) The warning message concern the default directory, in a hard code 'Default config'. There is a story behind it.
To address your installation problem, for Linux, first should be:
- verify the existence of the file 'autosave_a.py' in the home folder pointed by GIMP at Edit>Preferences>Folders>Plug-ins;
- set the permission of that file so it can be executed as a program, since the plug-in don't do it.
Sorry if you already done that, then you have to furnish further info!