After getting virtually no help at all at my travel agency, I decided to swoop the net for the most reasonable prices, dates and suchlike. I’ll book my flight once I have confirmation of the safari booking I did today: 32 day from Johannesburg, via Kruger, Zimbabwe, Vic Falls, Malawi, Tanzania, Zanzibar and Serengeti to Nairobi. 
With that leg confirmed, I’ll be off to the on-line flight booking and set this trip in stone. 180 days to go.