I hope at least some people find this useful. It represents knowledge gained through trial and (a lot of) error!

The set-up, as it was:

• iPod Touch connected via Apple-certified cable to USB port. My music library is on that device.
• The iPhone paired via Bluetooth.
• Occasionally, I wanted to use CarPlay; for that I connected via cable. No wireless Carplay in this model.

The issues:

1. Clumsy screen layout for iPod control via Duo Touch screen.
2. Very laggy control of the iPod. So bad, that often I was not sure that I had made a selection and so tried again but finished up selecting whatever was coming up next on that position on the touchscreen.
3. CarPlay would not consistently connect. Sometimes it would connect 2 times in a row on one journey (eg outbound but with a stop), and then not connect on the return journey. Sometimes it would connect for a number of journeys and then not at all for a few following journeys.

What was tried:

• #1 & #2 above were accepted as the reality of an RRS.
• The dealer tried multiple fixes to CarPlay, including new software and hardware. None made a material difference.
• I checked all the recommended settings on iPhone, including turning on Siri.
• I tried multiple different ways of connecting, eg different cables, trying both USB data ports, connecting the phone before starting car, after starting but before the Infotainment system had fully loaded, and afterwards, etc. Sometimes it connected, but not always.

What I discovered:

• It seems that if the Bluetooth connection to the iPhone is established on start-up, then it will not connect to CarPlay.
• I connected the iPod to the car via Bluetooth. Voila! The screen layout was much cleaner, and control was no longer laggy.
• The RRS will only connect to one Bluetooth device at a time. It sees the Bluetooth-connected iPod as a phone.
• I connected the phone via USB and voila! CarPlay came up instantly. I have been using it like that for over a week and it has been rock solid.
• This however means the phone needs to be connected each time by cable. Not a major issue for me.

I cannot claim that I have found the definitive, or even the best, solution but the results so far are promising.

One other, but unrelated, tip… If you change your email on the Land Rover InControl account, you cannot log into the car’s navigation profile. The emails do not match and there is no known option to update the email address in the car profile. Spent hours with JLR customer support, with no success. Again, by trial and error, I discovered that you can create a new profile in the car, with your new email address, and then log onto the In Control account. Your settings and history are preserved. You can then delete the old profile and, if you wish, rename the new one to the old name.
Hope this helps! MY21.5 HSE 221KW D16
Gone:
F15 30D X5
E70 30D X5
E53 30D X5
Jeep Grande Cherokee v8