A Royal Navy officer's MA thesis, from 2013, taken when at Staff College, which appeared last month on the BSAP History website. I did a quick read and it helps to give a different perspective, in part as several BSAP veterans were interviewed.

The academic title is: Consider the British South Africa Police contribution to counter insurgency operations, and how far was this successful?

The Abstract states:
In the aftermath of recent campaigns there is a debate over the military centric approach to counterinsurgency, with suggestion that the utility of police forces is not fully recognised nor correctly applied. This paper examines the Rhodesian counterinsurgency experience, considers contemporary counterinsurgency theories and explores the contribution of the British South Africa Police (BSAP), Rhodesia’s paramilitary police force. It concludes that police contribution through a population centric approach to counterinsurgency provides the most effective means for a government to provide security to its people and maintain its legitimacy through the rule of law throughout. The paper also examines the specific military functions that the BSAP achieved, identifying where these were appropriate and where they created a disadvantage.
The file is too large to upload alas, please Message me and include an email address to enable dispatch.

Added as Rhodesian COIN has attracted a lot of views on two or three threads: 366k on the main thread is:Rhodesian COIN (consolidated thread, inc original RLI)