The locations are very accurate. Portobello Road Market can be seen as Patrick Allen and James Maxwell track the doctor to his surgery, which is just off Portobello Road. The market ( which was then a normal market with some second hand stalls and shops) can be seen. The extra's were clearly normal members of the public who can be seen watching the filming and showing surprise as they walk into shot. The Dr's wife catches a 15 bus from Ladbroke Road ( which runs parallel to Portobello Road) alighting at Horse Guards, then walking to St James Park. The No 15 ran at the time via Ladbroke Grove through Trafalger Square. The Dr takes a taxi and catches a bus in order to meet with his contact. He alights at Halfpenny Steps (a pedestrian bridge, now replaced, across Regents Canal) in Maida Vale on the other side of which was the now demolished, Wedlake Street 'Baths' (swimming pool, baths and wash house) featuring the denouement of the film. In reality this is only a 10/15 minute walk from 'his' surgery but as a spy he is no doubt (unsuccessfully) ensuring he is not followed.
