Thanks guys. It's not the best sat nav in the world (however it's still better than the stock option for reasons mentioned above), but the main brief was get it as OEM looking as poss. I'd love to throw in a more modern Android tablet, which would be even better if I could tether it to my iPhone so it was "smart", but it's finding one with the right dimensions, screen in the right place, and has an AV input for a reverse camera. Tall order...