Fix + hint for others
So, after a bit of hacking about the following came up:
Firstly - a bit of RTFM:
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If you can not find any solutions to the problem you are having, you can enable the "Show Errors" flags located in /main.inc.php:
#Don't display errors
ini_set('display_errors',0);
ini_set('display_startup_errors',0);
Change this to
error_reporting(E_ALL);
ini_set('display_errors',1);
ini_set('display_startup_errors',1);
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Secondly, after reading through the code, I found that with my particular hosting solution, the "out the box code" was incorrectly calculating the directory... and hence wasn't including the config file.
I simply redefined this manually in the code and it now works.