How to send a parcel to South Africa from the UK?

I would like to send a parcel from the UK to South Africa but have no idea what I have to do in order to do this. The parcel is about 1kg in weight, 24cm long, 16cm wide and 6.5cm tall. The person who I am sending the parcel to, says that he has two addresses for the same house, but I should use his PO BOX one if I want to send a parcel. The address I have been given is PO BOX 60912 Pierre van Ryneveld 0045. I would like to know if this is the address I should use to send a parcel, what the format of the address should be, what stamps I would have to use in order to send it quickly and roughly how much it would cost to send it. Any help at all would be great and I am obviously clueless. Thanks!