I have modified sites_switch.php in the multisite module addon to allow it to work woith either subdomain or sub folders.

usage
- for subdomains: name the site config file as shown in the posted directions ie subdomainname_config.php eg london.tickets.com_config.php
- for sub-folders: name the site config file domainname_subfoldername_config.php eg tickets_london_config.php

This patch will ignore the subdomain config file if a subfolder config file exists.

I'm new to this stuff so use at your own risk and as they say around here, backup 1st.