Thanks for all the tips.
I've had a good look at the cheap and cheerful dignital GPS devices on Ebay. Charging them with a USB is probably not much more convenient that having my phone charging via the 12v socket.
i've managed to get my excellet Wye phone cradle in a decent HUD-esque position and my phone sideways.
I'm going to try WAZE for combined route planning with mini-speedo plus traffic camera warnings and, for known routes where I just want a normal lookinig speedo, I'm going to try Speedometer Simple (free app, but with ads presumably) for the time being.
Thanks everyone!
