after much digging around I have discovered that [civcicrm.files] is set incorrectly for some reason during install.
i'm hoping this will go some way to explaining the odd and inconsistent system status behaviour i am seeing around system status messages
I've found a post here Set [civicrm.files] explainig how to set the variable during via the civicrm.settings.php file
still doesn't seem to have fixed my problem though so I am wondering if I have set the values correctly.
Do I need a '/' on the end of either / neither / both path and url?