Why do some sites not have any ownership details?
The Land Registration Act 1988 came into force in 1990, allowing anyone to inspect registered titles and obtain information. In the 1990s it became mandatory to register all land in England and Wales when certain events occurred, like when land was sold.
Therefore if there is a parcel of land that does not have a polygon it can mean that there has been no sale of the land since the 1990s.
You tend to see land such as railway stations/lines, some roads that have no ownership details because of the reason above.
Within the platform, while a parcel of land may not have a polygon we can check if it has any planning applications matched with the address.
These are shown via the Properties Shown section - a yellow marker on the map will indicate that there is a planning application on that property. Simply click on the yellow marker and the information panel will open. You can then see the address and scroll down to the planning history section.
As for the railways, these sites are usually owned and managed by Network Rail, so I would suggest reaching out to them directly.