Spooks (2002) - 2 questions

Question: "Spooks" is called "MI-5" in the US. I'm aware that Five operates something like the FBI and Six like the CIA, however, what are One through Four?

Answer: They no longer exist. The Military Intelligence groups first appeared at around the time of the First World War. MI-1 was the original directorate, MI-2 dealt with the Soviet Union and Scandinavia, MI-3 with Germany and Eastern Europe, MI-4 handled aerial intelligence gathering, MI-7 dealt with propaganda, MI-8 with communication intercepts, MI-9 with covert operations, MI-10 were the technical experts, MI-11 dealt with security issues out in the field and so on and so forth. All these departments have either been shut down or subsumed into the Security Service, informally referred to by its original designation of MI-5, the Secret Intelligence Service, referred to as MI-6, or GCHQ, the Government Communications Headquarters.

Question: In this episode, Patrick McCann and his IRA splinter group plot to blow up "Broad Street Station" in London. In reality, British Rail beat him to it years ago. The real Broad Street Station closed in 1986, and has since been demolished (an office complex now stands on the site). Does anyone know which railway station (or stations) posed as the fictional Broad Street Station in this episode?

Answer: The shots of the tube station closing and the shot of the concourse were shot at Marylebone station. There is also a shot of the tracks in which a sign is visible pointing to Southwark station and the Jubilee Line, and I suspect this is a stock shot filmed at Waterloo station.