When I want to change the mirror I am using for updates, I can open the Software Centre, and go to Edit->Software Sources, and from there select another server.
This then goes through my /etc/apt/sources.list file, and replaces all the instances of the old mirror URL, with the new mirror URL.
If, however, I want to do this on the command line (perhaps I'm not running X, or I'm connecting over ssh), I have to go through the /etc/apt/sources.list file myself and change each instance.
This isn't the hardest thing to do, and of course I can do a search and replace, but it is a lot more work than just clicking the name of the server I want, plus it requires me to know a bit about the syntax of the sources.list file, and make sure I don't make an error while editing it.
Is there a command line program which can perform the same task as the Software Centre, and change my update mirror, without me having to edit this file?