I had heard that it referred to a old English flop house where one could purchase anything one desired, for a price. And if a person expired on site, he or she would be dropped through a hatch into the River Thames to go drifting with the tide.
The song does not in any way conform to Matty Groves.
The chord sequence and melody are interesting and alluring, often used for other songs, such as Amazing Grace and Oh, Little Town of Bethlehem.
That’s interesting! Always loved this song and how mysterious it was.