Mike,
unfortunately Charlestown is no longer used as a commercial port though it does see a fair bit of use as a film set.
I must find a picture of the entrance lock gates to this port, the way in is so tight and tortuous that you would never believe ships of this size could negotiate it.
It was a truly wonderful place to watch ships berth and load china clay the old fashioned way. The lorries would come along the high level road to right of picture and tip their load down the chutes to fill the ship by gravity.
regards
John J.