Your furniture is probably going in a container to South Africa as part of a 'groupage' consignment(ie sharing a container with other LCL [less than container load] consignments also bound for SA). While it may have been 'stuffed' in the box at Hull and sent on a feeder ship to Rotterdam, it was might also have been sent in a truck, by ferry to the Dutch port and put in a groupage box there. Your shipping agent, haulier or removals firm should be able to help you to track your consignment.