I wanted to see where all the Screwfix locations were in the South of England (don't ask), and I found that they don't have a general map on their site, just a list by alphabetical order, with London and the rest of the South of England separately. Since I live close to the edge of the M25, having the two separate was a pain.
So I cut and paste all the postcodes into a spreadsheet, uploaded them to Google Fusion Tables (take a look) and then used a little bit of Google map incantation to produce
Update 26/08/2019 - as you can see, this map is no longer working. I deleted the underlying Fusion Tables data in preparation for the "turn down" of the Fusion tables function. This page will now end up being used as a test page for mapping experiments in the forthcoming months.