This is an experimental map using Google Fusion Tables to display the localtion of (almost) every listed building in Great Britain. It has a few known issues, including the fact that the markers are sometimes not clickable, and there are some buildings missing.
These are limitations of Fusion Tables, and not something I can fix here. But there are no other freely available mapping products capable of displaying upwards of half a million markers on one page, so it's still better than nothing.
The map only shows the first 100,000 items in the visible window, so the overview can be a bit misleading. Once you start zooming in to lower levels then more buildings will show up.
For an overview of all the properties in the database, then try the heatmap visualisation.