The duo join The Thick of It star Peter Capaldi, who was confirmed as a new cast member for series two earlier today.
Romola Garai, Dominic West, Ben Whishaw, Anna Chancellor and Julian Rhind-Tutt will all return for the second run of the 1950s newsroom drama, which picked up warm critical praise for its first outing in the summer.
Tointon (The Inbetweeners) is cast as a club hostess who catches the eye of Hector Madden (West), while Tom Burke (State of Play) will play an industry rival and love interest for Bel Rowley (Garai). Capaldi plays Randall Brown, a new eccentric head of news at the BBC.
The six new episodes will feature the broadcast team "deeply embroiled in cover-ups, sexual intrigues and the resurgence of Mosley's fascism" and will have the "looming spectre of the Cold War" as its backdrop.
Filming started earlier this week in London and the second series is expected to air in summer 2012.
> 'The Hour' star Romola Garai confirms series two details
> 'The Hour' calls time with 1.7m