Well .... strange happenings. While driving to the VW specialist (on Saturday) the Nav was playing up - poor-to-nonexistent GPS signal, which I attributed to meteorological conditions, so resorted to road signs. When we arrived at the destination town I searched the address on Apple Maps on iPhone and found no problem with GPS signals - but I couldn't connect to carplay, which had never been a problem in the past. Annoyingly the dealer was closed, but looked to be a very promising setup. So we decided to try again today.
Thinking about the Carplay and GPS problems, plus earlier thoughts that the problem had occurred after a software update, I decided to look into the updates. I went into the engineering menu and selected software update. Not much happened for a minute or two, so went back to the menu to try a couple of other entries. All seemed fine so exited the engineering menu. The system rebooted, taking longer than it had in the past, and low-and-behold I was asked which multi media I wanted to connect to and was able to reconnect carplay.
Later we set off again to the VW specialist. GPS was now fully functional and there was no warning triangle or "please visit workshop" message.
Thinking this was all down to an update that hadn't been fully installed or a further (corrective) update that had partially downloaded and installing. As the WSBK riders all say -we'll see.