It is fairly easy to identify limestone features on an OS map. The names of features are shown on the map, eg Raven Scar or White Scar Caves. You can also see intermittent drainage patterns as the rivers/streams (blue lines) appear to start and stop randomly on the map.
Where there are blue lines, the rivers/streams are flowing over impermeable rock. Where there are no blue lines, the streams are flowing over limestone as they have disappeared through the permeable rock and are flowing underground.
You know you're looking at a limestone landscape when you see a limestone pavement.
Intermittent drainage is a good indicator of a limestone landscape. Because limestone is permeable, water is able to pass through it until it reaches impermeable rock and must re-emerge.
Shake holes are formed in limestone landscapes when boulder clay is washed down through cracks or gaps in the underlying limestone.