LONDON, Sept 4 (Reuters) – The bulk of Angola’s crude oil cargoes for October loading have been sold, traders said on Thursday, while business remained somewhat slower in the Nigerian market. Around 10 of Angola’s 55 cargoes are unsold, traders said, down from around 15 two days ago. More favourable refining margins and cracks compared to the September trading cycle have encouraged buying, particularly of heavier grades. Nigerian crude differentials remained under pressure and cargoes s