SOLVED !
Thanks everyone for the suggestions.
The answer is indeed to remove an entire layer from the map. Go to "Map Layers" and untick the "Places along the road". That removed all the icons from the map display
I had thought that it was possible to remove, say, the restaurant icon from the map and leave, say, the petrol starion icon, but it seems to be an all or nothing option.
If you do need to find a petrol station, restaurant etc, there is another option that lets you go in and scan a list of these, or, it would be easy to put them back on the screen temporarily by going back to "map layers" and reticking the "places along the road" box
thanks again
PS: very much enjoying the Jazz. The only thing I needed to do after getting it was to go on to ebay and buy a secondhand full size spare wheel and jack to replace the bottle of gunge (mine has the wheel well that is big enough to take a full size spare)