In the end it simply took another mug of tea and the rain ceased, allowing play to commence. I just needed more confidence in the art of the infusion.
I could agree that it would be possible to do the job in 30 minutes if you had proper hydraulic ramps, air tools etc. And weren't squashed between the car and the wall. With the vehicle being down on its bump stops, I couldn't get the trolley jack under it without removing its wheels and driving the car onto a plank.
It's moderately accessible:

Getting the dead one out required all of my amateur gynaecological skills to avoid dismantling the brakes / suspension or knackering anything.

Anyway, job done, nobody died, it self levels again without any leakage and I even remembered to torque up the wheelnuts (140Nm). Now I just have to figure how to repurpose the £700 I saved from the clutches of the BMW garage.
The worn area is pretty visible. Not v impressive after 4 years / 42k miles….

I can't imagine the Chinesium replacement could be any worse, the bar having been set pretty low to start with.
Now I can go and get that £10 Xmas tree, reduced from £70….
Murray