My parents were downgraded F to J DXB-LHR recently. Compensation was difference in fare paid and a voucher for J return LHR-DXB. No amount of effort persuaded them to offer a return in F. J might sound OK but is not worth much if you are 80+ and the whole point of shelling out for F was to be able to lie flat.
Compensation rules change with departure point - my guess is consumer protection is less robust in Africa than other parts of the world.