Ok, so after having a good look around I discovered two very good guides that helped me most of the way there:
This basically covers everything except for how to host your sysprep.inf file on the WDS server and how to modify it so that the machine name becomes the name that you've given it in Active Directory when it joins the domain. For that information I used this page:
On that page they give you a hint about where to put the file on the WDS server, and to use %MACHINENAME% as the computer name in the inf file.
What I did was to run setupmgr.exe on the machine being prepped, generated the inf file, then moved it off the machine to the server. I didn't leave a copy on the machine. I then sysprepped and copied the image to the server as described in the guide. After doing that I created the folder structure as mentioned in the second page and put the sysprep.inf file there. I then modified it so that the computer name had %MACHINENAME% in it.
Lastly, just for kicks, I generated my own unattend.xml file using Windows System Image Manager and this guide for helpers:
But mainly I tried to keep to the structure of the file in the second page as some of the settings are superfluous to an XP install.
I hope this helps someone. It turned out that doing it this way is a lot easier than the old RIS way, apart from the fact that you have to install XP from a cd onto the staging machine rather than using the generic install that RIS provided.