is it possible to have a seperate box, away from my map, which will cover the whole of my map?, skyboxes i heard they are called, will somebody explain?

What you're talking about is a "portal sky." "Skybox" refers to an "infinitely-far-away" box that appears wherever you place a sky shader in your map. It's just the 6 images that make up the sky (up, down, left, right, front, and back images, combined to a 360-degree panorama). Now, a portal sky can be created by cuilding a separate mini-map underneath your main map and placing a misc_skyportal in the box. For a detailed description, see this site (http://levelforge.teamhuh.com/forgelink/viewtopic.php?t=113&sid=051618f51d3895878916126599984bba).