Thanx for your reply Stevie, after talking to Navman the 600 series Navman units need 240v or 12/24v to operate, so are not handhelds like the 510 & 520. Iv looked at the TomTom rRider which looks ideal but I dont want a unit shaped like the other TomTom units as the're tooo bulky.
The Navman iCN is the ideal size weight, and the 520 has more advanced mapping software. They are also looking at bike mounts as they are receiving an ever increasing demand for them.
I shal go for the Navman iCN 520, unless anyone has other suggestions....
Tim

Aka SpeedDemon
Sussex