I'm glad you asked, as it prompted me to look back through the thread.
The information was given by Maggie Holland herself, in 2004:

Subject: RE: A Mr. Harding sort of England . . ?
From: GUEST,Maggie Holland - PM
Date: 15 Jul 04 - 04:49 AM

Back to the original question for a moment - yes, the "Mr Harding" in "A Place Called England" is indeed a reference to my earlier song "A Proper Sort of Gardener". Mr Harding was employed as a gardener for many years by Courages Brewery in Alton, Hants. He tended several gardens of houses that were owned by the brewery, including the one that I lived in as a child. The last time I met him was when I was visiting my parents' grave in Alton (in the early 80s, I think) and although long retired he had chosen to keep gardening by helping to keep the cemetery tidy.