There are 45 stations along the northwest coast, and most of it is walkable, although some stretches are still under development. 

Walks along along the Lakes Line, Furness Line or Cumbrian Coast Line (linear and circular).

Guided walks along the lines from the Leeds-Settle-Carlisle, Leeds-Morecambe and other selected Railways.

Walks along the mid-Cheshire line, which runs from Manchester towards Chester (linear and circular).

Walks along several lines in Lancashire and Greater Manchester (linear and circular).

This site includes information about walks around Lancashire, Cheshire and Manchester. Northern Rail is the rail operator in along several lines in the Northwest.

The Settle to Carlisle Way is a long-distance path following the railway line.  It is marked on Ordance Survey maps.  This web page, from the Long Distance Walkers Association, includes useful information, but the gpx file is only accessible to members.

FoSCR run guided walks from the Settle to Carlisle stations.

Three walks from Shrewsbury, Wellington and Telford stations.

13 walks from and between stations in the Lake District, with maps and descriptions.

Eco Escapes are all about travelling light and treading carefully in the stunning rural landscapes of Lancashire. They are about leaving the car at home and taking the time to explore new places by public transport, on foot or by bike. They are about discovering the county’s wonderful natural environments and the wildlife that makes its home there. 

A more detailed railwalk from Silverdale to Carnforth

https://www.discoverbowland.uk/itinerary/lancashires-wildlife-rich-limestone-coast/