The character Justine Lord plays here - someone close to, but not involved with the main suspect, primarily interested in Simon Templar (going so far as to getting into his private room/residence), and supporting him upon his arrival - is almost identical to the one she had just played in her previous appearance in the series, The Saint Steps In (1964)
The reason Tempar's standard Volvo P1800 isn't seen is simply because he's he's undercover as he investigates, and pretends to be someone else (his typical alias, 'Sebastian Toombs'), and doesn't wish to give any hints of his actual identity.
When Mandy asks Simon what he would like to drink he answers "Anything not shaken or stirred;" referencing the popular line from the contemporary Bond movies. Although Roger Moore later played Bond, he never used the phrase in any of the movies made during his tenure as the secret agent.