I tried that and still the same issue. I guess that I must accept that it won't work. I have a working sat nav in my jeep, but am trying to create something with trucker friendly navigation just for when I tow my caravan. I am too mean to pay the exhorbitant prices both new and second hand for the real thing!
This was my wife's old navigon and so perhaps I will park that and move onto something else.
I have just read your interesting dissertation on Binatone sat navs, and you can pick up a reasonable one of those for fairly small money. From your experience are there any particular models to steer away from?
Thanks for all your help, much appreciated.