Two more thoughts:
It is quite possible that the various individual tickets for a through journey were handed to the passenger loose in a little envelope style wallet, rather than actually being stapled together as a book. This might have been because they were card, rather than paper.
Remember that exchange controls existed for many years so paying for as much as possible, not just tickets, but also hotels, meals, etc., in sterling before you left meant that you had more money to spend on your pleasures. I believe that the controls existed, with varying limits, from 1947 to 1979, except for 1959 to 1966.