I was actually hoping to be able to get hold of a combined sharks fin for both radio and sat-nav. Içe seen a few cars with only one antenna but now understand that the sat-nav can be on the windscreen.

If you have a Columbus retro-fitted the sat nav GPS aerial can be fitted anywhere INSIDE the dashboard. It does not go on the windscreen. It normally just goes above the glovebox.

It has a Columbs fitted as OE