Thanks for the tip but it is a bit of a catch 22 situation. You have to receive a TA before you can adjust the volume ) I have an appointment with my dealer soon and maybe, maybe they will help. I rather doubt it though.
I'm sure it's in the settings somewhere as well. It's hard to find though as the normal settings icon always gets you to the basic audio set up and nothing else. I don't think it's got advanced audio like navigation volume or announcements volume.
There is an infotainment manual as well as a user manual. Worth checking the glovebox as if it's a new car they should be in there and shrink wrapped.