As default when you are viewing the OS Maps on your GPS Device Street labels are displayed showing you street names.
If you find these labels get in the way and you want hide them from the map page this can be done as follows.
Goto Setup - Map - Advanced Setup
Zoom Levels - Street Labels
From here you can change the Auto Setting to Off which will now hide the street labels from view.
Also if you have a GPS Device that came with pre-loaded Geocaches and want to hide the Geocache treasure chest Icons from the map view you can from Zoom Levels - Geocaches turn off the Geocache view.