Having looked into this further, it would appear that Microsoft Windows CE 6.0 is an 'embedded' product used by developers for mobile, smartphone, portable media and even modified Xbox game consuls.
But it still doesn't answer my original request as to whether I should purchase a system using this O/S, compared to perhaps other 'branded' sat navs.
I would add, that I have a number of Navman Pin 570 hand held sat nav type devices made for the French and German market, which could have their mapping change for UK use. these seem to use a O/S perhaps similar to MS CE 6.0.
The viewing screen of the sat nav as to be a minimum of 5", larger would be better. So any recommendations would be appreciated?.