I used ViewRanger as my app of choice for walking 5,045 miles around the entire British mainland coast. My published routes have been corrected for a few errors I made, but I didn't always make the perfect choice & my route might not be the best path to use.
For more info & details of a BOOK NOW AVAILABLE visit GBCoastWalk.com
Please read the notes with each route. Each has a summary of the terrain to expect & whether any named trails are used.