Thanks guys. Seems like the easiest way to bring up extra comps is to double-click the required comp in the project panel, which granted is easier but not necessarily obvious... We live and learn!
Now, why have the comps thumbnails in the project panel been made monochromatic? Finding the project panel more difficult to 'read' at a glance. Bring back the colourful comp thumbnail please, or at least an option of having it like the old version.