Ok - thanks. I have changed the 'lifetime' fluid a couple of times now but never gone as far dropping the cover to access filter which is not listed as a service item. Presume there is one in there on my model but will check further.
The first change was 53k and oil was a little murky but nothing serious. On the 2nd change @ 68k the oil appeared perfect but I will continue to change every few years anyway.
I noticed that "lifetime" fluid, in the BMW's acceptance it's about 150k km or 100k miles, because is what they expected as lifetime for a regular model! The Zed, being a collectible will jump over the rules and needs replacement of the "lifetime" fluids.
I had a friendly argue with a friend, working in a BMW workshop and I found these values written, when you look better in the inspection's schedule.
It's applying to the differential too. And to the Lambda sensor (Oxygen sensor).