Oil for the Rover Autobox seems to be almost a religion.
Here are the oils recommended for the Jaguar X-type, which
uses the exact same box
Plenty to choose from:
https://www.carid.com/jaguar-x-type-transmission-fluid/
So if you live in France, or anywhere else for that matter, plenty of choice, if your thinking cap has been put on properly.
Nothing special about that box, AT ALL!!
Otherwise only flagellation remains.
Here is something about the JATCO box as used in the Rover and MANY MANY other cars:
https://procarmanuals.com/jatco-jf50...service-group/