I've found a published list of OCs, which was published in the defence force journal
Militaria in 1985.* It gives Col Jopp's dates as 7 August to 5 October 1942.
Here's the page :
It's incomplete, as it omits the first Disso, Lt Col Shadwell.
*
http://scientiamilitaria.journals.ac...e/view/473/506