I'm working on a mod, and the layout itself is finished. However, whenever i go 'ingame' and look around the layout, which is an interior area, when i go north or south along corridors after a certain distance i'm teleported back the the entry point at the centre. Am i hitting the worldspace barrier for the area, and if so, can it be extended/enlarged?

Hmm... Normally if you walk outside the cell (like TCL through a wall) into open space it teleports you back in. There is a limit to the size/length of a cell. It is 32000 units. So you cannot place an object at X:32000 Y:32000 Z:32000 because it messes up havok. But usually doing this would make the game throw your entire level into one big jumbled mess, showing something is obviously wrong. I would say you left some markers or something over from a cell you copied. Unless you made one from scratch. And no this 32000 limit cannot be extended as it is hardcoded into the game engine.