We think that iFootpath is the best walking guide app for the UK due to the detailed descriptions and detail GPS map - but if you want to explore the UK on foot we would also suggest the following Apps in addition to iFootpath.
iWalk Cornwall is an app providing GPS-guided circular walks, with detailed directions and local information based on your current location.
Both the app and walks are designed and developed in Cornwall and have a big local following. Routes are continually being checked and updated with help from the local community. iWalk Cornwall was Highly Commended in the 2017-2018 Cornwall Tourism Awards and a finalist in the 2017 Cornwall Sustainability Awards.
The app is free to download. Walks are purchased for £1.99 from within the app which includes ongoing free updates. The "Lanhydrock Gardens" walk is included with the app for free so you can try it out, and there is a simulation mode so you can do so without driving there.
Over 200 walks are available in all areas of Cornwall, classified by steepness and length and themes such as coastal walks and pub walks. New walks are also continually being added.