Ok, I found the FAQ's which include 6 different methods to pair a phone and a satnav.

Which is the best method to connect the devices?

When pairing intercoms with two other 20s users should they also have the same pairing combinations set up?

We have just finished a trip but had a few niggles with the group intercom, one user had audio fade out while another had sat nav commands which stopped the intercom.

Music sharing was also not possible. I am sure it's just a matter of setting up the correct pairing with all devices.