Some that I have enjoyed:

• A Spy Among Friends
• Slow Horses
• The Ipcress File (both the recent TV show and the 1965 film are great)
• Traitors (2019)
• The Night Manager
• London Spy
• The Game (2014)
• Tinker, Tailor, Soldier, Spy (both the TV show from 1979 and the 2011 film are great)
• Smiley’s People