The gunners are a mixture of Jacklex and Scruby figures. Jacklex never produced any Boer gunners commercially although apparently some prototypes were made – click here. The Jacklex figures in this crew are BW6 Horse Holder and PEA5 Officer (from the Mexican War range).
There is good news on the Boer artillery front however as Newline Designs have just released a Pompom gun and crew. I already have a couple of Pompoms from Raventhorpe Miniatures but this newer offering looks a bit more businesslike so I will probably get some in due course.