Did a lot of research on this.
A number of company's do after market kits for MB's.

This will give you a matching colour/material pad to go on the dashboard plus the cellular mute cable loom.

By using the pad and the correct cable it looks very origional and there are no wires in sight.

Look at UK Supplier -

Dash Mount


The cable can be set up to auto-mute the phone and use the cars existing speakers.

I have purchased a Nokia 8210 which has voice dialling and this allows the user, with a single button push, to safely make or receive a call.

I am going to fit the whole system over Xmas and will write up my experiences.

Mike