Both the Surlemonts article and the Lanchester section in B. T. Whites British Armoured Cars 1914-1945 list the breakdown of each model. This breakdown for the production vehicles is as follows:
Mark I - 18
Mark IA - 4
Mark II - 7
Mark IIA - 6
Total - 35
In addition, Surlemont states that there was 2 prototypes (D1E1 & D1E2) and 2 instructional vehicles (D1E3 & D1E4) while White simply states that there was four prototypes.
Surlemonts article gives a detailed breakdown, by WD number, of the final location/user of 38 of the armored cars. Data for one Mark II is missing