Hi again,
The answer is yes, and no ! You cannot delete the networks. As you found out, deleting the network ,deletes the router !!
Are you autodiscovering ? or inputting a seedfile of routers ? Either way , once you have discovered the devices, you can use the View > Hide Objects menu item to hide all the networks, and then you probably want to group the routers into regions or customers ? In that case you can Edit > Add > Location. Add a box called London or UK , then you can drag and drop all your routers for that region into the box. Hope that helps