Hi Neil,
I bought a Quadlock
http://www.quadlockcase.com/ phone case and dock. Seems to be cheapest and most authentic on their website. They do 2 different tupes of mounts for the car, one as a dash/screen suction mount and one as a stick on quad lock. Both twist onto the phone case, or adapter you need to buy for the phone.
I got the wall mount version as it was the smallest and most unobtrusive mount, meant I didnt have to stick a big mount arm on the screen or dash, but simply twist the phone onto a clip.
Got mine today and installed on my mk5 and it works a treat!