I understand the reluctance to see PROW markers as wayspots, but around a year ago Niantic surprised most people (including me) by finally saying they were eligible.
The original thread was lost in the revamp but the official guidance is at Wayfarer Criteria Challenge - #6 by NianticTintino
PROW markers are eligible. Not guaranteed and not automatically good wayspots, but certainly eligible.
This is in the countryside at the edge of moorland. Admittedly with a road ending at that point, but a small quiet dead-end road - which also makes this an access point which i have used myself several times.
[edited for lots of appalling typos]