To reiterate: Where does one buy tickets? Do you have to go all the way to the port? Are there local places, in London, where one can buy tickets? (A travel agent?) Can one buy tickets in advance, or does one only buy a ticket for the very next ship?
I've Googled variations on "where to buy a ship ticket in victorian london" and I've read plenty of period literature, but somehow nobody ever buys a ticket in any of these stories; they just sort of turn up with tickets in their pockets.
Any suggestions for research material for late Victorian London is appreciated as well. I have Charles Booth's Life and Labour of People in London and I know about The Victorian Dictionary, which you'd think would be enough, but one can never have too much research.