On my Garmin Edge 800 I have the full GB 1:50000 scale maps (explorer?)
To plot routes I tend to use getamap to get the route down using the OS maps. At this stage though they are pretty much just lines of coordinates. I then export the TCX and take that into ridewithGPS. From there I then leave the off road bits alone but fix the road parts to "follow the roads". This then gives you a cue sheet that means you get turn by turn navigation on the road sections, and any of the complicated looking off road bits (bits where you think you might go wrong) I then add custom cue sheet entries that say stuff like turn right, turn left.
Yes this is a pain in the arse and I don't do it for every route and often I'll do something in between what I have described.
EDIT: I'm someone who was very happy with map and compass as well, but getting the Edge 800 and not having to stop and do all that with the map is very convenient.