Sorry Darren I've stolen your picture because I've noticed you have one like me. On the dash there is a white disc that looks like something slots into it. l used to have one on the dash but it was broken but l do have one in the rear by my sliding door. I'd be interested in knowing what it's for.
That makes sense though not that o have one in the rear. I did at first think it could be a holder for a vase.