Africa is the real trick. When it comes to getting there, the word cheap is seldom in the same breath. If it is, it'll still cost you.
Considerations. I have more logistical confidence in European ops over ADD ops. ie The fewer African ops, the smoother your business will be. I'd avoid Egypt altogether for a while.
*A. SN is a popular means to get to all of the francophone locations (no Ghana or SA) n/s from BRU. A lot of missionaries do this routing. Maybe that means something about affordability.
ST. AF does the same from CDG plus SA. KL has fewer possibilities.
OW. BA does it all from LHR but no DRC.
Getting between the African nations gets complex.
SA is a statistical/geographic outlier. Everything else is routine going through Europe. SA adds significant time and distance and the SA n/s service from the US Eastcoast becomes really nice.
The crews are good, the lamb stew ubiquitous and good, and the seats suck, on Kenyan.
IMO, KE service LHR-NBO is fine, but East Africa isn't in the OP's life so I wouldn't even bother with KE.