When I plug in my Mighty Mouse I get the toption in prefs to map a button to the Application Switcher, however these same options don't seem to be available when I use a multi button 3rd party mouse. Is there any way to get round this?
Check if the mouse has any Mac OS X firmware available - those usually include the ability to assign buttons to various tasks. If your mouse is from Kensington or Logitech, the company provides the firmware. If it's not a major brand, there is always USB Overdrive, which works with almost any mouse out there.