Inside the tower's dome are some separate triangular windows of clear glass, the view outside of the sparkling lights often follows the camera motion, revealing that they were superimposed later.
When Cyril first sees the tower there is a pan upwards, but the upper part of the tower doesn't quite 'stick' perfectly to the lower part underneath the wide rim, revealing the upper part to be CGI, the lower part the real set.
When Madge first meets the doctor after he crashed to earth in his spacesuit, it was 1938. The passage of time revealed 3 years. When Madge received the telegram her husband was lost, it was dated 20 December 1940. Finally, when Madge was interrogated by the Androzani miners, she stated the year was 1941. Either the telegram is incorrect, or the year of the first meeting as well as the response to the Androzani interrogation was incorrect.
The time frame is variously referenced as 1940 and 1941. The Lancaster Bomber, flown by Madge's husband, did not enter operational service until 2 March 1942.