Their entrance was amazing, the clothes they wore suited them perfectly.
Culture wise they are no different to many British girls, apart from the odd lapse into an accent.
I don't see what the fuss is about, all housemates represent themselves, and themselves alone.

As to them being Nigerian, of course they are, they come from Nigerian parents.
It's like saying Cliff Richard or Joanne Lumley and many many more people born abroad aren't British.