Be careful. The rules on using non permeable driveway coverings have changed. You can't just slap down more tarmac in most cases I think. We have just installed permeable bricks to ours - they look like normal bricks but apparently they soak water through.
You could just gravel it though. That might be easier. Just put a strip of wood (or small blocks half sunk) at the end to contain it and pour on top. Rake to flat.