How do I know if the the equalisation manouvre (whatever it is called) actually happened?
I have the Mark 1 (non facelift) model. On that, the MG logo LEDs go solid when balancing (as opposed to "breathing" when charging). I think that the dash will show 100% and not charging, but to see that without disturbing the balance charge you have to be at the driver's window looking in, and use the key fob lock button to turn on the display. Do NOT unlock as that will temporarily stop the charge, and it may not resume the balance after the 30 seconds.
You could also check the charge current reported by the EVSE, especially if it has a convenient WiFi connection and app. Unfortunately, if you charge at low power as I do, you may not notice the early balancing, which sometimes "limits" to some 4kW. I usually charge at 3.5kW max, to use up excess solar. But you will see the late part of balancing, where the car draws less than 400W, and way less than that goes into the battery.
On my MG4, I can use the app, which shows the power going into the HV battery. If you have a facelift ZS, you can presumably do that too. Unfortunately, it doesn't say that it is balancing. But it shows the estimated end of charge time as the same as the present time. This apparently happens only when balancing. My MG4 can balance at 80% etc. I don't know if the facelift ZS can do that.
After the charge is finished, I'm not aware of any way to tell that the balance has happened. I find that my ZS will often do a second balance charge, but I have to wait at least 10 minutes from the last attempt.