I've installed locally on my computer Magento 1.9.3 and then via composer have installed a couple of extensions.
Modules/Extensions are Fontis Australia Post and Better404.
They seem to have installed OK ,I can see them in the folders and in admin/System/Advanced/Modules Output.
BUT I cannot see them anywhere else in admin to enable them.
Can any one advise on this
If you check (on backend) into System - Configuration -> Advanced -> Advanced you'll see the full list of modules available on your Magento instance (available and installed).
Did you saw your modules there?
Sorry. At some point my brain forgot the part when you said "I can see them in the folders and in admin/System/Advanced/Modules Output." (my bad)
In that case your modules are correctly installed.
If you aren't being able to see the modules on your backend, maybe you can run these checks:
I've logged into my local MAMP Apache server logs and have a number of errors all with this same line
[Tue Nov 15 16:53:32 2016] [error] [client 127.0.0.1] client denied by server configuration: /Applications/MAMP/htdocs/Magento-1-9-3/site/app/etc/local.xml
File permission for local.xml is -rwxrwxrwx
Here is that Magento-1-9-3/site/app/etc/local.xml maybe there is an issue here?
<date><![CDATA[Thu, 03 Nov 2016 02:52:46 +0000]]></date>
<initStatements><![CDATA[SET NAMES utf8]]></initStatements>
That's not a real error.
Short version: the local.xml file could be accesible from the outside but the .htacess rule blocks the file to avoid being read.