Update.
On the basis of help from this thread which Wapping kindly opened for me I have ordered a Carpuride thing.
I shall of course blame you people when I forget to remove it and it goes missing.

Expect lots of 'Why won't my Carpuride thing connect to my phone/Sena? Why can't I hear the navigation instructions even though it says it's connected? Which is better, Kurviger/Cali Moto/Something else?' type questions. I'll probably use Google Maps through the winter when I'll be on my scooter and see how that goes.
I don't have a power source for my phone on the bike so in the short term I plan on using a power bank in the tank bag.
Seriously though, thank you all for your help and input, including Wapping for opening the thread for me.
Edit: I managed to connect my phone to my Sena intercom yesterday and have watched a number of videos about how to use the new device in preparation for it's arrival.