Below are new heatmaps of the locations of Greggs and Pret a Manger eateries in the UK. The locations are extracted from the Food Standards Agency's food hygiene rating data.
This is an entirely unoriginal concept, copied from Tom Forth's 2014 'eatmap' – except I've used Leaflet instead of the Google Maps API.
You can download the location data underlying the heat maps in CSV format: Greggs + Pret.
When I originally produced these maps in 2021, about 22% of the FSA records were missing location coordinates. For purposes of the heatmaps, I reduced that to about 2% by adding postcode coordinates from the ONS Postcode Directory. Since then, the geocoding at source has improved – as of June 2023, only about 10% of records are missing location coordinates, and I have again reduced that to about 2% by adding postcode coordinates.
See this 2021 FT article and Tom Forth's Twitter thread for context on the retail battle between Greggs and Pret a Manger.