Thanks Murdo. I either had a senior moment or I was looking at another posting where the user had not activated the "My location" feature, hence nothing to click and anyway I was looking for a menu item to get the overall UK map rather than an individual.
But,having clicked on my own "my location" the map has no pins for anyone. I tried Chrome instead of Firefox and just the same. On IE8 the map goes blank when zooming in.
I've now found my last year's post (via my profile). It was in the Feedback Section, but was not visible when I looked yesterday as I didn't notice that the default is to show posts from the last 2 weeks ("Thread Display Options") and there is only 1 post + a sticky in that period.
Last year Ben said he would look into it. But since no one has brought this up since then, I think it must be a very low priority. And it may not be easily fixable.