JH,
The flying in Botswana is all VFR so an IR is not essential. Ultimately the air charter companies are looking for guys who'll fit in with the other pilots and who'll have a good way with the clients.
Whilst it's likely any company that's interested in you would take you up for a test flight to check you can fly, you'd end up doing a minimum of 50 hours flying into the Okavango delta and its bush strips before you'd be let loose.
I know of a number of CPL onlys who've done a couple of seasons and then polished the IR off. To a certain extent, with an extra 1000 hours under your belt, the IR should be a lot more straightforward.
At times there can be upwards of 20 guys looking for work and maybe only a couple of jobs coming up, then it becomes a case of keeping your spirits up, staying positive and believing in yourself.