bowlingball

Recently bought an F Type coupe. Amazing car, but with an irritating fault. When the satnav gives spoken instructions, it does not mute the radio, so the two compete with each other. Having previously owned an XF and an XK, both of which automatically muted the audio when the sat nav 'spoke' I can only believe this is a fault. The dealer has sought an answer to no avail, but has confirmed it occurs on all of their F types. Any other F type owners seen the problem and/or found a solution?