Interesting?, although I doubt it was used as a run up light, such as the HID fitting had, I’m wondering if this was some form of low level night lighting?

Cool! Looks pretty old, must be an early 80's fitting at the latest. I wonder if that starter is for the 8W tube given it's proximity to it? If not I would have said perhaps the 8W is for a sustained emergency light (where the main tube is for mains lighting and a supplementary tube provides non maintained EM lighting), but of course if that starter is for the 8W then that rules it being an emergency lamp out.