I never cease to be amazed at the quality of workmanship, depth of knowledge and sheer ingenuity that goes into this project; I am looking forward to watching it all go back together.
Re. the steering wheel, isn't the wheel fitted to the Taunton scrapyard example different to the others which you have used for reference? -It appears to be have been made out of steel, with a separate rim, rather than cast in one piece in aluminium. Perhaps the need to protect steel spokes from rust might explain why they are coated as well as the rim in this case?
It is difficult to be 100% certain but the spokes of the wheel in the old photo of the tipper look as if they are bare aluminium. Also, if the aluminium spokes were once coated, then in the case of the bus in the museum, somebody has gone to a lot of trouble to remove every trace of the coating from the spokes, before wrapping the rim.