I have Garmin Edge 1000 with OS 50K. I cannot get Basecamp to allow me to use the routing tool on the off road cycling routes (Green hollow circles on the OS Map). Any ideas?
A direct route doesn't really use anything. Having created it you can follow it on a GPS even without a map. Clearly if you have a map loaded the route will show on top of that.
The OS maps as they are not routeable are just a picture or more correctly a back drop to any route you setup. I find it easier to use the New Track when working with OS maps as you can then click anywhere you like, i.e. on the cycle routes. This will create a *.gpx file that can be sent to your device.