A new map is available showing campsites in England, Wales, Scotland and Northern Ireland within a short distance of railway stations. Several of these are just a short journey from Manchester and you can use the map to search for campsites within 3km of stations or between 10-20km away.
This is the link to the Rail, Hike Camp map:-
https://felt.com/map/Rail-Hike-Camp-kv9BQ3TnpTvud8TM43gTqpB?lat=50.945444&lon=-2.666219&zoom=9.923