definition of CIVICRM_UF_BASEURL causes problems on local network installation

I've installed Drupal and Civi on my local machine (using MAMP).
When I give my machine's IP to a colleague, he can't see CiviCRM.
This is because the link to Civi in Drupal becomes 'localhost', and he is not running a webserver on his own machine.

This appears to be caused by the setting of CIVICRM_UF_BASEURL in civicrm.settings.php.
I initially accessed and set up site through the URL 'localhost' on my machine, so this has been set as the site base URL, and so from another machine it can't work.
Drupal sets the base url as 'localhost' too, but is fine if accessed as a different URL, as it appears to check what URL the user is using to request pages.

I've changed the setting to my IP address, but I'm still getting problems with stylesheets and possibly javascript (eg, the admin page looks all wrong).