The social housing complex that Miller is living in is the Heygate estate at Elephant and Castle. You can see the Strata in one of the scene where Miller broke through some barricade to have the night view. The Heygate has since been demolished to make way for Elephant Park by Lend Lease.
Langdon mentions "Conolly's Great Game", this is a reference to Arthur Conolly's term that he coined in reference to the struggle between the British and Russian Empires over control of Central Asia.
Prior to filming, the training budget was slashed so Toby Kebbell paid for his own physical trainer, often under the supervision of screenwriter Robert Henry Craft (who is a former paratrooper).
The final gunfight scene is often cited in the top ever gunfights put on film for it's calm realism with no music score, realistic reloading and sound. The Director was inspired by the post bank heist gunfight in the film Heat and so all gunfire is live recorded and real with bullet impacts, as only blanks were used, being the only additional sound FX added in those scenes.