Thanks @pab567 the update worked eventually, but maybe a tip for the benefit of other newbies. It kept failing to start with and this was because I was getting to the update button via Settings and then scrolling down to system information and clicking the update button from there - this then brings up an error reading the card. Whereas, if you follow the advice (trust me to find a different approach that doesn't work) to just hold in the menu button for a few seconds and then go to update from there it works! Remains to be seen if the system will now be more stable and if it fixes the bug whereby when playing music via Bluetooth the track description gets stuck on the first track you play - 🤞