I do like that you used OSM rather than Google maps.
I should probably make the UX better. When you're on the heatmap page (or the distance matrix page), look at the top right of the screen. It shows you where it's basing its searches on, and you can override that bias with any location you like.
You only need to update it once per session - all pages and components will be updated
It added 50 grocery stores with a "nearby places" search and inhad to refresh the page to start a new search instead of spending time clicking those X's.