I know it is way out of the stated budget, but for a trip to Africa that may be a trip of a lifetime, I would seriously consider the Sigma 150-600 Contemporary. Quite a bit cheaper than the 100-400 II. Actually, new about the same or even less than a 100-400 MK I. Many people including myself think that the Sigma C is as good as the MK I 100-400 for image quality at shared focal lengths, plus it is 200mm longer. I would recommend the Sigma over the similarly priced Tamron, as the Sigma has the Dock option which allows you to adjust many of the lenses features, such as the focus limiter, OS performance as well as allowing AF microadjustment at four focal lengths, and four focus distances, giving a total of 16 AF adjustments. This could be useful on a 1200D which lacks AF Micro Adjustment in the body. The 150-600 Contemporary is the only lens in the Contemporary line that offers the full set of adjustments, they are normally saved for the Sport and Art lines.
I have not been to Africa myself, but all of the reports that I have read suggest that the shortest focal length that you want to take is a 400mm, even with a crop sensor camera. It is amazing sometimes how big you think something looks through the viewfinder, only to see that it is really small in the final image. The problem is that one tends to "focus" ones attention on the main subject making it seem bigger than it really is.
Alan