you could use an outside socket,if you put it on the side of the 'van you will have to drill a small hole through the side panel,failing that you may get it on the side of the bottle box and pass the cable through were the mains cables go through,if you drill through the side panel make sure you seal it well,this is less of an issue on the bottle box[but still needs sealing]on our last van did not have a external socket so took the co-ax direct from aerial through the vents in bottle box then connecting to another co-ax which i fed through as described above.