So I dug up the ol' gravitas solution and decided it was time to load a mesh in there. Coding4Fun again proved helpful. Unlike the very uninformative error messages from DirectX. With some playing about, I managed to get the sample heli.x to load and render in stark white.

Then I had to turn on the lights. (device.RenderState.Lighting = true; device.RenderState.Ambient = Color.White;)

For some reason my point list is now ignoring its colours and using the last one that heli did. Sheep.