Ok I've got a working wep.

my /etc/network/interfaces.

iface wlan0 inet dhcp
wireless-essid {my essid}
wireless-key { my hex key }

auto lo
iface lo inet loopback

////////////////

Then to start I run
$> ifup wlan0

and it starts up. Only thing I don't yet have is a way of making it vary (since I do move around a lot.)