I have not seen cyclestreets before. It looks really good, thanks.
It's quite handy to devise the route on RideWithGPS, then save the gpx file, and then imprt that file into Mapyx Quo, so you can print off OS maps with your route on. Dead simple and quick.Another vote for Ride with GPS and their default map. However it does have mapping errors, but no where near as many as Open Street Map or Open Cycle Map have (although they are getting better albeit slowly).
I also use Mapyx Quo (paid for) which uses OS mapping and easily knocks the crap out of anything web based, and Memory Map, Anquet and other standalone consumer PC software.