Nigel -
I sort of agree with you re Air Algerie, however suppose you could say many people take Emirares travelling SSE to then connect from Dubai ,then fly WSW to South Africa ?
Yes you have a good point in which case Algiers is exactly on track for South Africa. But I haven't ever see SA mentioned on any BHX forums. It's been about the States, the Far East and Australia.
If I was flying to SA from BHX I would look at a European connection first, not DXB.