I’ve worked with only a couple of map scripts - Google Map and OpenStreetMap - but not enough to figure out if there was a way to scale the markers based on the map zoom level. What looked OK zoomed in had overlapping when zoomed out. And when I made them smaller to look OK when zoomed out, were too small when zoomed in and got harder to see amidst the features. In the end it was a matter of compromise so it looked half-OK whatever the zoom level.
I was able to get much better results using the QGIS app, but AFAIK it doesn’t have a “save for web” feature.
That said, if I were interested in an event, I would want to be able to see / find the location without much trouble. “around the U.K.” sounds like a lot of territory is being covered. I don’t know how easy it is to get around the U.K. but I probably wouldn’t be interested in events I would have trouble getting to. So I would look at the map to see if there was an event near me, then if there was one, look at the table to see the details.