I'm having a go with Osmand on my Android phone, but am having trouble with the routeing thing.
I created a route using bikehike, exported it as a track, then got Osmand to work out directions based on it. I then clicked the blue arrow to get turn by turn instructions in my earphones. This sort of worked, but roundabouts weren't described correctly (turn slightly left, then turn slightly right rather than take 2nd exit). I did a bit of reading and decided a route would be a better thing, so got bikehike to export as a route, which seemed better, although it seemed stuffed full of waypoints, like every 50m or so. The route description in my ear was much better, but it the routing seemed to not follow the route I'd drawn using bikehike, if that makes sense.
Spurred on by this (limited) success, I tried it on the Mid Sussex Hilly with the gpx file supplied by Martin. OK-ish at the start, then again it moved away from the line on the map.
What am I doing wrong? (several things I suspect). At a first guess, bikehike is providing a route with too many waypoints in it. All help greatfully received.