I live in the States near Chicago and all I know about British English is through watching british TV shows - a lot!

It seems that a common expression there about someone that is a recluse is something like - "He keeps himself to himself."

Example:

Police investigator:  "Did you know the murdered woman next door?"

You:  "No, sir, not well at all.  She always kept herself to herself!"

This construction is not common in our side of the pond.

Be well.

CR