A good cheap site I have used and can recommend is Severn House Camping at Montford Bridge near Shrewsbury
https://www.severnhousecampsite.co.uk/Main/Home.html
£6 a night for a small tent, it's quiet, and The Wingfield Arms pub is on the other side of the bridge.
Interesting site, it is only a few miles from where I live. It is on a network of lostways, all of which could be significant LDW's, however it does serve the Severn Way. There is a grey path on my 1:25kOS map that leads right into the east of the site, it leads back to Bromley Forge. If the name is not enough to be proof of it's reason to be a right of way
what is.
The Wingfield Arms is an ideal pub for the hospitality dependent traveler, it has geared itself up for caravan trade after being a busy pub on the A5, right next to one of Thomas Telford's bridges over the river Severn, little over a decade ago this bridge was a death trap of heavy traffic, now it is quiet enough to stand over the center span and watch the water pass by. It is at the point, where the river first hits the sandstone of S. Cheshire and N.Shropshire and is deflected off it.
I wonder if the OP called in at the Star Inn Dyliffe on his Glyndwr's Way trip. Now there is pub that is remote enough to have rough camping spots very close by, the sort of place that could well be worth while calling up before arrival to see if they have suggestions. I may not have walked the GW, but many of my exploration lines have taken me there.
Are we walkers backward in understanding the power of the mobile phone as an itinerant's means of forward planning? Add to the list phone numbers, places like the Star Inn, whereas the Montford Bridge site will probably never see it's full potential as a cross roads of ways, recognizing the latter might help a small historical Inn survive.