Home Counties vs Britain

Home Counties and Britain both are nouns.

Word	Noun	Adjective	Verb	Adverb
Home Counties	Yes	No	No	No
Britain	Yes	No	No	No

Home Counties (noun)	Britain (noun)
the English counties surrounding London into which Greater London has expanded	a monarchy in northwestern Europe occupying most of the British Isles; divided into England and Scotland and Wales and Northern Ireland; `Great Britain' is often used loosely to refer to the United Kingdom