Today I've spent a little time adding two more details to the cab interior, specifically that big wheel (I'm assuming it's the brake), and the pipework that runs across and down the sides of the backhead. Unfortunately I didn't have any spare wheels of the right type or size so I had to knock one up from some brass wire. The pipework was at least nice and easy as I did have some small etched handwheels (on the same sheet from RT Models as the reversing lever) and the rest was just wire.
Again not necessarily an accurate rendition but they will do the job nicely. I may need to add a few more details but these will be fixed inside the upper plastic part of the cab so I think this finishes the backhead parts attached to the body casting.