The goldmine that is called Debian Administration has asked the question of how to install a local Debian mirror on your LAN. Enjoy the support!
From the question:
I'd like to install a local Debian mirror on my network so that as I experiment with different things (and break them) I can reinstall faster, as well as make new package installs that much faster (new gigabit switch and nics!)
I've tried apt-mirror but this keep getting an error on startup, and the docs are a little thin. Any suggestions?
Enjoy the answers at Debian-administration.org