If you cycle one of the long distance routes then you are advised to use one of Sustrans' award winning cycle maps. Based on Ordnance Survey data, they include just about everything you  need to follow a route.

Routes are well signposted, but inevitably can get turned around and you can just miss a sign along the way whether on a lamppost, direction post or painted on the ground. There is only so much physical signing that can be done, so take a map with you at least as a useful guide - not that you need to stick rigidly to a route but the map does give the safest sections. Often circuitous, but with safety and quiet as the main goal.

The maps have insets for some towns and cities for those tricky bits where more detail is needed, and also satellite insets that give you the broader picture of a route. 

You can buy the maps at many of the larger bookshops and also specialised, outdoor retail shops. Alternatively, click through to the Sustrans on-line store to order the maps.