G'day Dusky,

> Warning: file() [function.file]: URL file-access is disabled in the server configuration in
> ..../includes/modules/shipping/austpost.php on line 88
> Is this telling me it's a server issue and if so how do I get around it?

Yes, that is a server issue.
The Australia post module has two different methods of of contacting the external servers, the FILE method (which is being denied by your hosting company), or the cURL access method.
You can select which method to use from the admin pages. There is a tickbox to enable/disable cURL. If it is disabled, the FILE method will be used.

I suggest you try enabling cURL.

Cheers
Rod