The song being sung in the Russian nightclub is the Russian ballad "Dorogoi dlinnoyu", better known as the 1968 English version "Those Were The Days" sung by Mary Hopkin.
Kenneth Williams, (who became a regular in the "Carry On" movies), makes a brief uncredited appearance in this movie.
The aircraft-type that figures so prominently in this movie (as early product-placement?) is the twin-engined Airspeed "Ambassador" airliner that was being operated at the time in small numbers by British European Airways (as its "Elizabethan" Class) on the "Silver Wings" service from London to Paris. Despite its popularity with travellers, the good-looking plane was soon eclipsed by the new "Viscount" turbo-prop, a type that had superior performance.
The full version of this movie is one hour and forty-two minutes, rather than the one hour and twenty-seven minute version normally shown on U.K. television, which is missing all of the scenes featuring Laurence Harvey, which were cut for the U.S. release. The missing segments have been edited back into a version that was originally transmitted on C4 in the U.K.