thank you lazyweb; A number of folk have written to me pointing out Netem. One in particular, Yusuf Goolamabbas even provided a set of wrapper scripts for Netem that I'm going to be digging into next week.

Netem is built around various lower level tools like tc, which is good (tc is what I was using year ago). I'm hopeful it will be really easy to use, and will blog something when I've used it in anger :)