Locate your HQ on a OS Map & a Street Map
OS Maps of your local area & Street Maps of your local area
Split Cubs into work groups and issue each group an OS Map and also a Street Map
Ask each Cub to locate their road on both Maps and then as a group ask them to locate the Scout HQ.
Get each Cub to then track the route they would take to get to Cubs using the OS Map and explain to the leader what Map Symbols they pass along the way. (If they don't pass any, point out some random ones on the map.