How to Map Surname Distributions from the 1939 National Register

1. Search for the exact surname in the 1939 register on Findmypast.
2. Cut and past the result column into a spreadsheet choosing the paste option that formats into columns. You will have to do this in batches of 20.
3. Insert a header row. Give the county column the title Location.
4. Add a column filled with the number 1 and give it the title Value.
5. Save the spreadsheet
6. Go to http://www.openheatmap.com/
7. Click on Upload and wait for the result. It may return a diagnostic indicating edits you may need to make to the location names. Otherwise you'll see a map preview with formatting options.

The example is for males named Northwood, 265 individuals. There is no indication on the map of how many people are at any particular location.
Click on
http://www.openheatmap.com/view.html?map=VpScombriformessRubblier to see the display made dynamic so that it places pins on the map year by year according to birth year. To do that label the birth year column on the spreadsheet Time.
If you're skilled at working with spreadsheets you can use the free Open Heat Map to produce a map coloured according to the number of occurrences in each county. Make a separate sheet with each row a county and the value column containing a count of the number of people recorded there. Open Heat Map has several interesting capabilities which could be applied to other data sources such as FreeBMD.
If you try this please post a comment on your experience.