Tracing Ownership of Land

[SBDFHS]

One of my FHS members is trying to trace the ownership of some land that is not shown on the Land Registry. He has managed to trace definite ownership up until the late C19th and possible ownership to the mid 20th century but cannot prove anything. It may have been included in a property sale as an "etc." so the person who owned it may not have been aware of the fact.
Would anyone on this board be able to suggest anything or be able to offer help?

Thank you