This map shows all the English places called Marston, or with 'Marston' in their name. Considering it is an Anglo-Saxon name (marsh farm) it's not surprising that they are all in the central strip.
I've grouped close huddles of Marstons into just one marker to avoid cluttering the map. So for instance the northern outpost Long Marston in Yorkshire also refers to Marston Wyes in its marker.
In the markers, some of the place names are hyperlinked to their Wikipedia entry.