Attack of the Cybermen - S22-E1
Visible crew/equipment: Just after the Cyber Leader orders that Flast be thrown out of the refrigerated room, one of the floor crew can be seen kneeling behind some crates. (01:20:50)
Attack of the Cybermen - S22-E1
Revealing mistake: When Lytton stabs the Cybercontroller, some of the Cybercontroller's 'blood' gets splashed on the camera. (The 'blood' is green-dyed water spraying from the Cybercontroller's arm.).
Attack of the Cybermen - S22-E1
Plot hole: The junkyard at 76 Totters Lane seen in "Attack of the Cybermen" was also in "An Unearthly Child", the very first episode of the show. If you consider London's high land value, it is highly unlikely that an ownerless junkyard would still survive twenty-two years... the local authority would have long since issued a "compulsory purchase order".
Answer: In 'The Five Doctors', three separate Cyberleaders are definitely used. So it's likely that Cyberleaders are like unit commanders, of which a fair-sized army might have several.
Daria Sigma