Thanks for all the help, suggestions and especially links! Looks like I'm going to be busy with this for the forseeable future. I've attached a pic of the work-in-progress - luckily Stafford Castle was never much more than a baronial keep, so it was quite small and difficult to defend. It was basically lots of octagonal towers and not much else. I've done the roofs and foundations and I'm doing the windows at the moment. When it's done I'll post it in the gallery :o)