Scenes are included showing filming of Carry on Cabby (1963), including a clapper board with that title. However, this movie was produced as "Call Me a Cab". The title was changed after production was completed.
The Ford Cortinas in the Carry on Cabby (1963) scenes are the wrong type. In the real film they are Consul Cortinas which have white oval front lights that double as sidelights and (white) indicators, whereas in this reconstruction of the scene the cars are the later post-1964 model which have separate rectangular sidelights and amber indicators, and a different radiator grille.
The Hoover Dirtsearcher Junior vacuum cleaner Hattie was using did not go into production until 1969.
Some items on the set were from the 1970s.
During the filming of Carry on Cabby (1963), in the scene where Hattie's character introduces herself to her female cab drivers, the right-hand of the three Ford Cortinas clearly has a fake numberplate that has slipped down at one side, revealing the car's real numberplate underneath.
The red Jaguar E-TYPE or XKE that John drives Hattie home in when they first meet is a 2+2 model with a small rear bench seat and higher roof line. The tax disc in the window clearly shows that it expires in 1963. However the 2+2 model was only available from 1966.
The story allegedly takes place in 1961 but a car's tax disc clearly shows December 63; not only that, scenes show the filming of Carry on Cabby (1963) (also from 1963).