There is an app produced by Bike Hub, which is "the UK cycle industry's levy scheme" - basically it's funded by the cycling industry. As well as a bike shop finder (of dubious usefulness, in my experience), it has a route planner/satnav with voice instructions. It allows you to select start and finish points for a journey, then it calculates a route itself, taking into account cycle-specific information and gives you a choice of quitest/fastest/balanced routes, avoiding hills wherever possible. It's not possible to plot waypoints, so you can't do a circular route, you can't change the route once calculated, and some of the choices it makes are dubious - on one route I tried it wanted to take me down all sorts of backstreets and shared pavements to avoid a perfectly safe main road. Nice idea, but poor execution, IMO.
Instead, I use BikeBrain which has a nice map feature. It caches the maps beforehand, so if you know the area you'll be heading and preview the map before heading out, it will show you where you are on the map as you ride. Of course, you have to have a fair idea of which direction you need to be heading, and there's no voice instructions because there's no planned route.
There are various route planners online (e.g. bikehike, mapometer), but I'm not aware of any that let you transfer the routes to a smartphone.
