Applied the basic materials to the bike, got the colour scheme kind of how I want it. Experimenting with mia_material and tweaking it seems to have got rid of a lot of the "cartoony" feel I am trying to avoid (Fresnel reflection and anisotropy especially). Render times (preview: final gather 640 by 480) are around 30 seconds on my system which I can live with.

No scene lights, only using an HDRI forest scene from Dan Mayer (smashmethod).