With a bit of effort, I have finally got my head around using Google MyMaps. This is an extension to Google Maps that allows you to overlay points of interest (POIs), photographs and route information on top of Google Maps. This aids navigation and can be used to record locations on your journey for future reference.
Here is the MyMaps I used for the North Sea Cycle Route. It shows campsites, photographs (automatically geotagged), Ferries and other POIs.
Click on these links to interact with the map. You can switch each layer on/off and zoom into each country: