As you can see, although it is textured, the sky box isn't. Also, the gaps are due to not rendering bezier splines yet - I haven't written any tessellation code yet. It looks quite a bit too bright and I'm assuming this is because I'm not using the lightmaps as yet. So, overall, it's rough but it's a decent start.
I have a lot of refactoring to do before I start adding more touches but it's going pretty well.
Thanks go to paradoxnj and others in the forum who helped me try to figure out some rendering issues that, as ever, turned out to be due to my own stupid idiocy!