Sorry, but Gordon doesn't really have the right footplate design (the curve is "upside down" and is too prominent). Also, the back of his chassis wouldn't fit anyway, since it's not 90°. Can't really think of an engine with a similar footplate design.
In Super's thread about Spencer's coaches, I remarked that their design and livery bore a slight resemblance to the Hogwarts coaches, and edited a different Henry image to look like the engine (except the external mods I mentioned in the comparison weren't as well done, and some were not even considered in that edit, such as the smokebox extension and tender walls):
Paint.NET's hue/saturation feature was used to make the green parts red, and it wasn't as good looking as the "pre-repaint" illustration in this thread. Also, since the Hogwarts coaches are not the same shade as the engine, all that would need to be done to Spencer's coaches would be to make the pink stripes yellow (or golden), add the Hogwarts Railways symbols, paint the roofs a darker grey and the buffers black. They are just the right shade for it.